Pepper Flash Mac: Fix crash when playing video on MB retina

content/browser/renderer_host/backing_store_mac.mm

Index: content/browser/renderer_host/backing_store_mac.mm
diff --git a/content/browser/renderer_host/backing_store_mac.mm b/content/browser/renderer_host/backing_store_mac.mm
index 5e17e5fe024ad3e1c31dedb141323be1ae0e64ed..19411393d7fa8c7be1fb82b4bb0d17819a0c20ec 100644
--- a/content/browser/renderer_host/backing_store_mac.mm
+++ b/content/browser/renderer_host/backing_store_mac.mm
@@ -87,9 +87,13 @@ void BackingStoreMac::PaintToBackingStore(
   gfx::Size pixel_size = size().Scale(device_scale_factor_);
   gfx::Rect pixel_bitmap_rect = bitmap_rect.Scale(scale_factor);
 
+  size_t bitmap_byte_count =
+      pixel_bitmap_rect.width() * pixel_bitmap_rect.height() * 4;
+  DCHECK_GE(dib->size(), bitmap_byte_count);
+
   base::mac::ScopedCFTypeRef<CGDataProviderRef> data_provider(
       CGDataProviderCreateWithData(NULL, dib->memory(),
-      pixel_bitmap_rect.width() * pixel_bitmap_rect.height() * 4, NULL));
+      bitmap_byte_count, NULL));
 
   base::mac::ScopedCFTypeRef<CGImageRef> bitmap_image(
       CGImageCreate(pixel_bitmap_rect.width(), pixel_bitmap_rect.height(),