Add multi-planar functions to GpuMemoryBuffer

cc/test/test_gpu_memory_buffer_manager.cc

Index: cc/test/test_gpu_memory_buffer_manager.cc
diff --git a/cc/test/test_gpu_memory_buffer_manager.cc b/cc/test/test_gpu_memory_buffer_manager.cc
index 7430051ea6ff16ad6d9160f8d6896b428be87d61..c90c09abf23a4c1ebc7f83672953a99197716aba 100644
--- a/cc/test/test_gpu_memory_buffer_manager.cc
+++ b/cc/test/test_gpu_memory_buffer_manager.cc
@@ -49,16 +49,25 @@ class GpuMemoryBufferImpl : public gfx::GpuMemoryBuffer {
     mapped_ = true;
     return shared_memory_->memory();
   }
+  void* Map(size_t plane_index) override {
+    CHECK_EQ(plane_index, 0u);
+    return Map();
+  }
   void Unmap() override {
     DCHECK(mapped_);
     shared_memory_->Unmap();
     mapped_ = false;
   }
   bool IsMapped() const override { return mapped_; }
+  size_t GetNumberOfPlanes() const override { return 1; }
   Format GetFormat() const override { return format_; }
   uint32 GetStride() const override {
     return StrideInBytes(size_.width(), format_);
   }
+  uint32 GetStride(size_t plane_index) const override {
+    CHECK_EQ(plane_index, 0u);
+    return GetStride();
+  }
   gfx::GpuMemoryBufferHandle GetHandle() const override {
     gfx::GpuMemoryBufferHandle handle;
     handle.type = gfx::SHARED_MEMORY_BUFFER;