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..cb53c205bbd5d026442f4d13df8a78d85da0b718 100644
--- a/content/common/gpu/client/gpu_memory_buffer_impl.cc
+++ b/content/common/gpu/client/gpu_memory_buffer_impl.cc
@@ -76,18 +76,27 @@ GpuMemoryBufferImpl* GpuMemoryBufferImpl::FromClientBuffer(
 }
 
 // static
-size_t GpuMemoryBufferImpl::BytesPerPixel(Format format) {
+size_t GpuMemoryBufferImpl::BitsPerPixel(Format format) {
   switch (format) {
     case RGBA_8888:
     case RGBX_8888:
     case BGRA_8888:
-      return 4;
+      return 32;
   }
 
   NOTREACHED();
   return 0;
 }
 
+// static
+size_t GpuMemoryBufferImpl::PixelsToBytes(
+    size_t pixel_count,
+    gfx::GpuMemoryBuffer::Format format) {
+  size_t size_in_bits = pixel_count * BitsPerPixel(format);
+  DCHECK_EQ(size_in_bits % 8, 0u);
+  return size_in_bits / 8;
+}
+
 gfx::GpuMemoryBuffer::Format GpuMemoryBufferImpl::GetFormat() const {
   return format_;
 }