Add support for PartionRealloc to return nullptr

Currently the PartitionRealloc code path will only exit, with no
option to return nullptr on failure, unlike PartitionAlloc code path.
This CL refactors the realloc code path to be similar to alloc code
path, following the upstream patch:
https://chromium-review.googlesource.com/c/chromium/src/+/1044971

This also changes the version of realloc exposed to third party C libs
to have the nullptr behaviour, like the exposed version of alloc.

This CL is a redo of
https://pdfium-review.googlesource.com/c/pdfium/+/31990

BUG=chromium:783022

Change-Id: Ib1b659079585dfd0423d683b8a2c7b6758a22a01
Reviewed-on: https://pdfium-review.googlesource.com/32613
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/core/fxcrt/fx_memory.cpp b/core/fxcrt/fx_memory.cpp
index 6a135ae0f8..006e03031e 100644
--- a/core/fxcrt/fx_memory.cpp
+++ b/core/fxcrt/fx_memory.cpp
@@ -35,8 +35,9 @@ void* FXMEM_DefaultCalloc(size_t num_elems, size_t byte_size) {
 }
 
 void* FXMEM_DefaultRealloc(void* pointer, size_t new_size) {
-  return pdfium::base::PartitionReallocGeneric(
-      gGeneralPartitionAllocator.root(), pointer, new_size, "GeneralPartition");
+  return pdfium::base::PartitionReallocGenericFlags(
+      gGeneralPartitionAllocator.root(), pdfium::base::PartitionAllocReturnNull,
+      pointer, new_size, "GeneralPartition");
 }
 
 void FXMEM_DefaultFree(void* pointer) {