cc: Fix BytesPerPixel issue and refactor.

cc/resources/resource.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_RESOURCES_RESOURCE_H_
 #define CC_RESOURCES_RESOURCE_H_
 
 #include "base/numerics/safe_math.h"
 #include "cc/base/cc_export.h"
 #include "cc/resources/resource_provider.h"
@@ skipping 33 matching lines @@
     base::CheckedNumeric<size_t> checked_value = BitsPerPixel(format);
     checked_value *= size.width();
     checked_value *= size.height();
     checked_value /= 8;
     return checked_value.ValueOrDie();
   }
 
   inline static size_t UncheckedMemorySizeBytes(const gfx::Size& size,
                                                 ResourceFormat format) {
     DCHECK(VerifySizeInBytes(size, format));
-    return static_cast<size_t>(BitsPerPixel(format)) * size.width() *
-           size.height() / 8;

[reveman, 2015/06/24 18:02:26]

hm, looks like this was broken for height < 8 before this, that's pretty bad.

[vmpstr, 2015/06/24 18:46:14]

I think the order of multiplicative operations is well defined to be left to
right, so this was probably OK. 

+    return (static_cast<size_t>(BitsPerPixel(format)) * size.width() *
+            size.height()) /
+           8;

[reveman, 2015/06/24 18:02:26]

Can you add a temporary bytes_per_row variable here to make this a bit easier to
read?

   }
 
  protected:
   void set_id(ResourceId id) { id_ = id; }
   void set_dimensions(const gfx::Size& size, ResourceFormat format) {
     size_ = size;
     format_ = format;
   }
 
  private:
   ResourceId id_;
   gfx::Size size_;
   ResourceFormat format_;
 
   DISALLOW_COPY_AND_ASSIGN(Resource);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_RESOURCE_H_