Update GPU memory buffers to use StrideInBytes internally.

content/common/gpu/client/gpu_memory_buffer_impl.cc

Index: content/common/gpu/client/gpu_memory_buffer_impl.cc
diff --git a/content/common/gpu/client/gpu_memory_buffer_impl.cc b/content/common/gpu/client/gpu_memory_buffer_impl.cc
index d3c08bdb1a09b0d1256c297148cd190d2fae5690..befde5e6837d402ccfc75337a6e0822131b0b401 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl.cc
@@ -5,6 +5,7 @@
 #include "content/common/gpu/client/gpu_memory_buffer_impl.h"
 
 #include "base/logging.h"
+#include "base/numerics/safe_math.h"
 #include "content/common/gpu/client/gpu_memory_buffer_impl_shared_memory.h"
 #include "ui/gl/gl_bindings.h"
 
@@ -76,16 +77,26 @@ GpuMemoryBufferImpl* GpuMemoryBufferImpl::FromClientBuffer(
 }
 
 // static
-size_t GpuMemoryBufferImpl::BytesPerPixel(Format format) {
+bool GpuMemoryBufferImpl::StrideInBytes(size_t width,
+                                        Format format,
+                                        size_t* stride_in_bytes) {
+  base::CheckedNumeric<size_t> w = width;

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

nit: maybe s/w/s/ for stride

   switch (format) {
     case RGBA_8888:
     case RGBX_8888:
     case BGRA_8888:
-      return 4;
+      w *= 4;
+      break;
+    default:

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

nit: please avoid having a default case as that allows the compiler to help
ensure we update this code after adding new formats. it's still nice to have the
NOTREACHED outside the switch statement in case format is somehow messed up at
runtime. maybe just keep this as before for now and put the IsValid check inside
the switch statement..

+      NOTREACHED();
+      return false;
   }
 
-  NOTREACHED();
-  return 0;
+  if (!w.IsValid())
+    return false;
+
+  *stride_in_bytes = w.ValueOrDie();
+  return true;
 }
 
 gfx::GpuMemoryBuffer::Format GpuMemoryBufferImpl::GetFormat() const {