cc: Fix BytesPerPixel issue and refactor.

cc/resources/resource_util.cc

Index: cc/resources/resource_util.cc
diff --git a/cc/resources/resource_util.cc b/cc/resources/resource_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..71141590e33d7711a5b24c655dac926bdafc4216
--- /dev/null
+++ b/cc/resources/resource_util.cc
@@ -0,0 +1,38 @@
+// Copyright 2015 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.
+
+#include "cc/resources/resource_util.h"
+
+#include "cc/base/math_util.h"
+
+namespace cc {
+
+// static
+size_t ResourceUtil::UncheckedWidthInBytes(size_t width,
+                                           ResourceFormat format) {
+  size_t bytes_per_row = width * static_cast<size_t>(BitsPerPixel(format)) / 8;
+  return bytes_per_row;
+}
+
+// static
+size_t ResourceUtil::UncheckedSizeInBytes(const gfx::Size& size,
+                                          ResourceFormat format) {
+  DCHECK(VerifySizeInBytes<size_t>(size, format));
+  return size.height() * UncheckedWidthInBytes(size.width(), format);
+}
+
+// static
+size_t ResourceUtil::UncheckedWidthInBytesAligned(size_t width,
+                                                  ResourceFormat format) {
+  return MathUtil::RoundUp<size_t>(UncheckedWidthInBytes(width, format), 4u);
+}
+
+// static
+size_t ResourceUtil::UncheckedSizeInBytesAligned(const gfx::Size& size,
+                                                 ResourceFormat format) {
+  DCHECK(VerifySizeInBytes<size_t>(size, format));

[ericrk, 2015/07/24 20:03:52]

Super nit (feel free to ignore): the following can still fail even if this check
passed or the caller pre-checked, as the rounded up width could cause math
overflow vs the non-rounded-up one used in the checks.

Same problem above, but almost impossible to hit, as you'd have to be within 4
of the limit.

[prashant.n, 2015/07/25 07:15:43]

Hmm, I'll check on this.

+  return size.height() * UncheckedWidthInBytesAligned(size.width(), format);
+}
+
+}  // namespace cc