Remove unused codepage from WideString::GetWideString().

Consolidate code into sole caller, which always retrieves a string
from the "default ANSI code page". Add unit test for this code path.
Fix sign extension bug giving bogus 0xffffff80 codepoint uncovered
by unit test on non-windows. Note windows result is different because
the system conversion routine does actually work.

Change-Id: I1c1246b203ee66e9ff0b6fccf97594788bcd0fca
Reviewed-on: https://pdfium-review.googlesource.com/39730
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/core/fxcrt/fx_system.cpp b/core/fxcrt/fx_system.cpp
index 27cbd65f3c..061ca6d82d 100644
--- a/core/fxcrt/fx_system.cpp
+++ b/core/fxcrt/fx_system.cpp
@@ -203,6 +203,7 @@ int FXSYS_WideCharToMultiByte(uint32_t codepage,
   }
   return len;
 }
+
 int FXSYS_MultiByteToWideChar(uint32_t codepage,
                               uint32_t dwFlags,
                               const char* bstr,
@@ -211,9 +212,8 @@ int FXSYS_MultiByteToWideChar(uint32_t codepage,
                               int buflen) {
   int wlen = 0;
   for (int i = 0; i < blen; i++) {
-    if (buf && wlen < buflen) {
-      buf[wlen] = bstr[i];
-    }
+    if (buf && wlen < buflen)
+      buf[wlen] = reinterpret_cast<const uint8_t*>(bstr)[i];
     wlen++;
   }
   return wlen;