Update GPU memory buffers to use StrideInBytes internally.

ui/gl/gl_image_memory.cc

Index: ui/gl/gl_image_memory.cc
diff --git a/ui/gl/gl_image_memory.cc b/ui/gl/gl_image_memory.cc
index 0a67e000665b6a5806a0f935f61e02faaf540a15..3879d30a641691ab51955900c508bbc152a32d73 100644
--- a/ui/gl/gl_image_memory.cc
+++ b/ui/gl/gl_image_memory.cc
@@ -100,18 +100,25 @@ GLImageMemory::~GLImageMemory() {
 }
 
 // static
-size_t GLImageMemory::BytesPerPixel(gfx::GpuMemoryBuffer::Format format) {
+bool GLImageMemory::StrideInBytes(size_t width,
+                                  gfx::GpuMemoryBuffer::Format format,
+                                  size_t* stride_in_bytes) {
+  base::CheckedNumeric<size_t> w = width;

[reveman, 2015/01/13 16:04:40]

nit: s/w/s/ for stride?

   switch (format) {
     case gfx::GpuMemoryBuffer::RGBA_8888:
     case gfx::GpuMemoryBuffer::BGRA_8888:
-      return 4;
+      w *= 4;
+      break;
     case gfx::GpuMemoryBuffer::RGBX_8888:
       NOTREACHED();
-      return 0;
+      return false;
   }
 
-  NOTREACHED();
-  return 0;
+  if (!w.IsValid())
+    return false;
+
+  *stride_in_bytes = w.ValueOrDie();
+  return true;

[reveman, 2015/01/13 16:04:40]

nit: would be nice to have a NOTREACHED check here in case format is an invalid
value at runtime. maybe move this IsValid code up into the switch statement?

 }
 
 bool GLImageMemory::Initialize(const unsigned char* memory,