Disable GWP-ASan on 32-bit Windows

When GWP-ASan is used with 32-bit address spaces, false positives are
much more common because a random bad dereference is much more likely to
point into the GWP-ASan region. After several months, the Windows/x86
version of GWP-ASan has not found bugs we couldn't find with the 64-bit
only version so disable it to reduce false positives.

Bug: 969146
Change-Id: I9beaa01b428c2fa6495c10f634cf9e01c3d170d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1696208
Auto-Submit: Vlad Tsyrklevich <vtsyrklevich@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#677071}

components/crash/content/app/run_as_crashpad_handler_win.cc

@@ -23,7 +23,7 @@
 #include "third_party/crashpad/crashpad/handler/user_stream_data_source.h"
 
 #if BUILDFLAG(ENABLE_GWP_ASAN)
-#include "components/gwp_asan/crash_handler/crash_handler.h"
+#include "components/gwp_asan/crash_handler/crash_handler.h"  // nogncheck
 #endif
 
 namespace crash_reporter {

components/gwp_asan/buildflags/buildflags.gni

@@ -4,11 +4,14 @@
 
 import("//build/config/allocator.gni")
 
+# Windows/x86 is disabled due to https://crbug.com/969146
+supported_platform = is_mac || (is_win && current_cpu == "x64")
+
 declare_args() {
   # Is GWP-ASan malloc/PartitionAlloc hooking enabled for chrome/ on a given
   # platform.
-  enable_gwp_asan_malloc = (is_win || is_mac) && use_allocator_shim
-  enable_gwp_asan_partitionalloc = (is_win || is_mac) && use_partition_alloc
+  enable_gwp_asan_malloc = supported_platform && use_allocator_shim
+  enable_gwp_asan_partitionalloc = supported_platform && use_partition_alloc
 }
 
 declare_args() {