Run clang-tidy modernize-use-auto on //third_party/pdfium

See the bugs and cxx post for justification and details:
https://groups.google.com/a/chromium.org/forum/#!topic/cxx/RkOHzIK6Tq8

This change was done using clang-tidy as described here:
https://chromium.googlesource.com/chromium/src/+/lkcr/docs/clang_tidy.md

Bug: chromium:776257
Change-Id: I1f6637cde8b3e41825993a736bed6763dd7beacb
Reviewed-on: https://pdfium-review.googlesource.com/19971
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

4 files changed, 26 insertions, 27 deletions

diff --git a/core/fxcrt/string_view_template.h b/core/fxcrt/string_view_template.h
index 12b422e090..fa33858a68 100644
--- a/core/fxcrt/string_view_template.h
+++ b/core/fxcrt/string_view_template.h
@@ -150,7 +150,7 @@ class StringViewTemplate {
   }
 
   pdfium::Optional<size_t> Find(CharType ch) const {
-    const UnsignedType* found = reinterpret_cast<const UnsignedType*>(FXSYS_chr(
+    const auto* found = reinterpret_cast<const UnsignedType*>(FXSYS_chr(
         reinterpret_cast<const CharType*>(m_Ptr.Get()), ch, m_Length));
 
     return found ? pdfium::Optional<size_t>(found - m_Ptr.Get())
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index bc0ad86297..97090cfadf 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -154,7 +154,7 @@ std::string WritePpm(const char* pdf_name,
                      int stride,
                      int width,
                      int height) {
-  const char* buffer = reinterpret_cast<const char*>(buffer_void);
+  const auto* buffer = reinterpret_cast<const char*>(buffer_void);
 
   if (!CheckDimensions(stride, width, height))
     return "";
@@ -451,7 +451,7 @@ std::string WritePng(const char* pdf_name,
     return "";
 
   std::vector<unsigned char> png_encoding;
-  const unsigned char* buffer = static_cast<const unsigned char*>(buffer_void);
+  const auto* buffer = static_cast<const unsigned char*>(buffer_void);
   if (!image_diff_png::EncodeBGRAPNG(
           buffer, width, height, stride, false, &png_encoding)) {
     fprintf(stderr, "Failed to convert bitmap to PNG\n");
@@ -644,7 +644,7 @@ int ExampleAppResponse(IPDF_JSPLATFORM*,
          GetPlatformWString(label).c_str(), is_password, length);
 
   // UTF-16, always LE regardless of platform.
-  uint8_t* ptr = static_cast<uint8_t*>(response);
+  auto* ptr = static_cast<uint8_t*>(response);
   ptr[0] = 'N';
   ptr[1] = 0;
   ptr[2] = 'o';
@@ -1249,8 +1249,8 @@ bool RenderPage(const std::string& name,
   if (!options.scale_factor_as_string.empty())
     std::stringstream(options.scale_factor_as_string) >> scale;
 
-  int width = static_cast<int>(FPDF_GetPageWidth(page) * scale);
-  int height = static_cast<int>(FPDF_GetPageHeight(page) * scale);
+  auto width = static_cast<int>(FPDF_GetPageWidth(page) * scale);
+  auto height = static_cast<int>(FPDF_GetPageHeight(page) * scale);
   int alpha = FPDFPage_HasTransparency(page) ? 1 : 0;
   std::unique_ptr<void, FPDFBitmapDeleter> bitmap(
       FPDFBitmap_Create(width, height, alpha));
diff --git a/third_party/base/allocator/partition_allocator/partition_alloc.h b/third_party/base/allocator/partition_allocator/partition_alloc.h
index 285f2af5a4..04ae17014a 100644
--- a/third_party/base/allocator/partition_allocator/partition_alloc.h
+++ b/third_party/base/allocator/partition_allocator/partition_alloc.h
@@ -534,7 +534,7 @@ ALWAYS_INLINE void* PartitionCookieFreePointerAdjust(void* ptr) {
 
 ALWAYS_INLINE void PartitionCookieWriteValue(void* ptr) {
 #if DCHECK_IS_ON()
-  unsigned char* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
+  auto* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
   for (size_t i = 0; i < kCookieSize; ++i, ++cookie_ptr)
     *cookie_ptr = kCookieValue[i];
 #endif
@@ -542,14 +542,14 @@ ALWAYS_INLINE void PartitionCookieWriteValue(void* ptr) {
 
 ALWAYS_INLINE void PartitionCookieCheckValue(void* ptr) {
 #if DCHECK_IS_ON()
-  unsigned char* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
+  auto* cookie_ptr = reinterpret_cast<unsigned char*>(ptr);
   for (size_t i = 0; i < kCookieSize; ++i, ++cookie_ptr)
     DCHECK(*cookie_ptr == kCookieValue[i]);
 #endif
 }
 
 ALWAYS_INLINE char* PartitionSuperPageToMetadataArea(char* ptr) {
-  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
+  auto pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
   DCHECK(!(pointer_as_uint & kSuperPageOffsetMask));
   // The metadata area is exactly one system page (the guard page) into the
   // super page.
@@ -557,8 +557,8 @@ ALWAYS_INLINE char* PartitionSuperPageToMetadataArea(char* ptr) {
 }
 
 ALWAYS_INLINE PartitionPage* PartitionPointerToPageNoAlignmentCheck(void* ptr) {
-  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
-  char* super_page_ptr =
+  auto pointer_as_uint = reinterpret_cast<uintptr_t>(ptr);
+  auto* super_page_ptr =
       reinterpret_cast<char*>(pointer_as_uint & kSuperPageBaseMask);
   uintptr_t partition_page_index =
       (pointer_as_uint & kSuperPageOffsetMask) >> kPartitionPageShift;
@@ -566,7 +566,7 @@ ALWAYS_INLINE PartitionPage* PartitionPointerToPageNoAlignmentCheck(void* ptr) {
   // the last index is invalid because it is a guard page.
   DCHECK(partition_page_index);
   DCHECK(partition_page_index < kNumPartitionPagesPerSuperPage - 1);
-  PartitionPage* page = reinterpret_cast<PartitionPage*>(
+  auto* page = reinterpret_cast<PartitionPage*>(
       PartitionSuperPageToMetadataArea(super_page_ptr) +
       (partition_page_index << kPageMetadataShift));
   // Partition pages in the same slot span can share the same page object.
@@ -578,7 +578,7 @@ ALWAYS_INLINE PartitionPage* PartitionPointerToPageNoAlignmentCheck(void* ptr) {
 }
 
 ALWAYS_INLINE void* PartitionPageToPointer(const PartitionPage* page) {
-  uintptr_t pointer_as_uint = reinterpret_cast<uintptr_t>(page);
+  auto pointer_as_uint = reinterpret_cast<uintptr_t>(page);
   uintptr_t super_page_offset = (pointer_as_uint & kSuperPageOffsetMask);
   DCHECK(super_page_offset > kSystemPageSize);
   DCHECK(super_page_offset < kSystemPageSize + (kNumPartitionPagesPerSuperPage *
@@ -590,7 +590,7 @@ ALWAYS_INLINE void* PartitionPageToPointer(const PartitionPage* page) {
   DCHECK(partition_page_index);
   DCHECK(partition_page_index < kNumPartitionPagesPerSuperPage - 1);
   uintptr_t super_page_base = (pointer_as_uint & kSuperPageBaseMask);
-  void* ret = reinterpret_cast<void*>(
+  auto* ret = reinterpret_cast<void*>(
       super_page_base + (partition_page_index << kPartitionPageShift));
   return ret;
 }
@@ -641,9 +641,8 @@ ALWAYS_INLINE size_t PartitionPageGetRawSize(PartitionPage* page) {
 }
 
 ALWAYS_INLINE PartitionRootBase* PartitionPageToRoot(PartitionPage* page) {
-  PartitionSuperPageExtentEntry* extent_entry =
-      reinterpret_cast<PartitionSuperPageExtentEntry*>(
-          reinterpret_cast<uintptr_t>(page) & kSystemPageBaseMask);
+  auto* extent_entry = reinterpret_cast<PartitionSuperPageExtentEntry*>(
+      reinterpret_cast<uintptr_t>(page) & kSystemPageBaseMask);
   return extent_entry->root;
 }
 
@@ -687,7 +686,7 @@ ALWAYS_INLINE void* PartitionBucketAlloc(PartitionRootBase* root,
     slot_size = raw_size;
   }
   size_t no_cookie_size = PartitionCookieSizeAdjustSubtract(slot_size);
-  char* char_ret = static_cast<char*>(ret);
+  auto* char_ret = static_cast<char*>(ret);
   // The value given to the application is actually just after the cookie.
   ret = char_ret + kCookieSize;
   memset(ret, kUninitializedByte, no_cookie_size);
@@ -737,7 +736,7 @@ ALWAYS_INLINE void PartitionFreeWithPage(void* ptr, PartitionPage* page) {
   CHECK(ptr != freelist_head);  // Catches an immediate double free.
   // Look for double free one level deeper in debug.
   DCHECK(!freelist_head || ptr != PartitionFreelistMask(freelist_head->next));
-  PartitionFreelistEntry* entry = static_cast<PartitionFreelistEntry*>(ptr);
+  auto* entry = static_cast<PartitionFreelistEntry*>(ptr);
   entry->next = PartitionFreelistMask(freelist_head);
   page->freelist_head = entry;
   --page->num_allocated_slots;
diff --git a/third_party/base/numerics/safe_math_impl.h b/third_party/base/numerics/safe_math_impl.h
index 5ad79ce192..4bcc67188c 100644
--- a/third_party/base/numerics/safe_math_impl.h
+++ b/third_party/base/numerics/safe_math_impl.h
@@ -59,9 +59,9 @@ bool CheckedAddImpl(T x, T y, T* result) {
   // it using the unsigned type of the same size.
   using UnsignedDst = typename std::make_unsigned<T>::type;
   using SignedDst = typename std::make_signed<T>::type;
-  UnsignedDst ux = static_cast<UnsignedDst>(x);
-  UnsignedDst uy = static_cast<UnsignedDst>(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux + uy);
+  auto ux = static_cast<UnsignedDst>(x);
+  auto uy = static_cast<UnsignedDst>(y);
+  auto uresult = static_cast<UnsignedDst>(ux + uy);
   *result = static_cast<T>(uresult);
   // Addition is valid if the sign of (x + y) is equal to either that of x or
   // that of y.
@@ -110,9 +110,9 @@ bool CheckedSubImpl(T x, T y, T* result) {
   // it using the unsigned type of the same size.
   using UnsignedDst = typename std::make_unsigned<T>::type;
   using SignedDst = typename std::make_signed<T>::type;
-  UnsignedDst ux = static_cast<UnsignedDst>(x);
-  UnsignedDst uy = static_cast<UnsignedDst>(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux - uy);
+  auto ux = static_cast<UnsignedDst>(x);
+  auto uy = static_cast<UnsignedDst>(y);
+  auto uresult = static_cast<UnsignedDst>(ux - uy);
   *result = static_cast<T>(uresult);
   // Subtraction is valid if either x and y have same sign, or (x-y) and x have
   // the same sign.
@@ -163,7 +163,7 @@ bool CheckedMulImpl(T x, T y, T* result) {
   using SignedDst = typename std::make_signed<T>::type;
   const UnsignedDst ux = SafeUnsignedAbs(x);
   const UnsignedDst uy = SafeUnsignedAbs(y);
-  UnsignedDst uresult = static_cast<UnsignedDst>(ux * uy);
+  auto uresult = static_cast<UnsignedDst>(ux * uy);
   const bool is_negative =
       std::is_signed<T>::value && static_cast<SignedDst>(x ^ y) < 0;
   *result = is_negative ? 0 - uresult : uresult;
@@ -308,7 +308,7 @@ struct CheckedLshOp<T,
   static bool Do(T x, U shift, V* result) {
     using ShiftType = typename std::make_unsigned<T>::type;
     static const ShiftType kBitWidth = IntegerBitsPlusSign<T>::value;
-    const ShiftType real_shift = static_cast<ShiftType>(shift);
+    const auto real_shift = static_cast<ShiftType>(shift);
     // Signed shift is not legal on negative values.
     if (!IsValueNegative(x) && real_shift < kBitWidth) {
       // Just use a multiplication because it's easy.