Temporarily turn off the memory-zeroing optimization on macOS.

It is breaking macOS GPU tests.

Bug: 890752
TBR: ajwong
Change-Id: I3f686473483cab053fc43e3d4b719a2900bdd71b
Cq-Include-Trybots: luci.chromium.try:mac_optional_gpu_tests_rel
Reviewed-on: https://chromium-review.googlesource.com/1255592Reviewed-by: Chris Palmer <palmer@chromium.org>
Commit-Queue: Chris Palmer <palmer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595654}

base/allocator/partition_allocator/partition_bucket.cc

@@ -478,7 +478,11 @@ void* PartitionBucket::SlowPathAlloc(PartitionRootBase* root,
       PartitionExcessiveAllocationSize();
     }
     new_page = PartitionDirectMap(root, flags, size);
+#if !defined(OS_MACOSX)
+    // TODO(https://crbug.com/890752): Remove this when we figure out and fix
+    // whatever is breaking on macOS.
     *is_already_zeroed = true;
+#endif
   } else if (LIKELY(this->SetNewActivePage())) {
     // First, did we find an active page in the active pages list?
     new_page = this->active_pages_head;
@@ -510,7 +514,11 @@ void* PartitionBucket::SlowPathAlloc(PartitionRootBase* root,
       void* addr = PartitionPage::ToPointer(new_page);
       root->RecommitSystemPages(addr, new_page->bucket->get_bytes_per_span());
       new_page->Reset();
+#if !defined(OS_MACOSX)
+      // TODO(https://crbug.com/890752): Remove this when we figure out and fix
+      // whatever is breaking on macOS.
       *is_already_zeroed = true;
+#endif
     }
     DCHECK(new_page);
   } else {
@@ -520,7 +528,11 @@ void* PartitionBucket::SlowPathAlloc(PartitionRootBase* root,
     if (LIKELY(raw_pages != nullptr)) {
       new_page = PartitionPage::FromPointerNoAlignmentCheck(raw_pages);
       InitializeSlotSpan(new_page);
+#if !defined(OS_MACOSX)
+      // TODO(https://crbug.com/890752): Remove this when we figure out and fix
+      // whatever is breaking on macOS.
       *is_already_zeroed = true;
+#endif
     }
   }
 

base/allocator/partition_allocator/partition_root_base.h

@@ -10,6 +10,7 @@
 #include "base/allocator/partition_allocator/partition_bucket.h"
 #include "base/allocator/partition_allocator/partition_direct_map_extent.h"
 #include "base/allocator/partition_allocator/partition_page.h"
+#include "build/build_config.h"
 
 namespace base {
 namespace internal {
@@ -141,6 +142,11 @@ ALWAYS_INLINE void* PartitionRootBase::AllocFromBucket(PartitionBucket* bucket,
   }
   PartitionCookieWriteValue(char_ret + kCookieSize + no_cookie_size);
 #else
+#if defined(OS_MACOSX)
+  // TODO(https://crbug.com/890752): Remove this when we figure out and fix
+  // whatever is breaking on macOS.
+  is_already_zeroed = false;
+#endif
   if (ret && zero_fill && !is_already_zeroed) {
     memset(ret, 0, size);
   }