Reland: GpuMemoryBuffer interface change: Map(**) to Map() and memory(plane); stride(plane)

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 7f6e8d1999d80374d32d6aec546befaffe129ded..78fa6ad5aab4d3e8bc62deef44436131d7711673 100644
--- a/cc/test/test_gpu_memory_buffer_manager.cc
+++ b/cc/test/test_gpu_memory_buffer_manager.cc
@@ -23,22 +23,19 @@ class GpuMemoryBufferImpl : public gfx::GpuMemoryBuffer {
         mapped_(false) {}
 
   // Overridden from gfx::GpuMemoryBuffer:
-  bool Map(void** data) override {
+  bool Map() override {
     DCHECK(!mapped_);
     if (!shared_memory_->Map(gfx::BufferSizeForBufferFormat(size_, format_)))
       return false;
     mapped_ = true;
-    size_t offset = 0;
-    int num_planes =
-        static_cast<int>(gfx::NumberOfPlanesForBufferFormat(format_));
-    for (int i = 0; i < num_planes; ++i) {
-      data[i] = reinterpret_cast<uint8*>(shared_memory_->memory()) + offset;
-      offset +=
-          gfx::RowSizeForBufferFormat(size_.width(), format_, i) *
-          (size_.height() / gfx::SubsamplingFactorForBufferFormat(format_, i));
-    }
     return true;
   }
+  void* memory(size_t plane) override {
+    DCHECK(mapped_);
+    DCHECK_LT(plane, gfx::NumberOfPlanesForBufferFormat(format_));
+    return reinterpret_cast<uint8_t*>(shared_memory_->memory()) +
+           gfx::BufferOffsetForBufferFormat(size_, format_, plane);
+  }
   void Unmap() override {
     DCHECK(mapped_);
     shared_memory_->Unmap();
@@ -46,12 +43,10 @@ class GpuMemoryBufferImpl : public gfx::GpuMemoryBuffer {
   }
   gfx::Size GetSize() const override { return size_; }
   gfx::BufferFormat GetFormat() const override { return format_; }
-  void GetStride(int* stride) const override {
-    int num_planes =
-        static_cast<int>(gfx::NumberOfPlanesForBufferFormat(format_));
-    for (int i = 0; i < num_planes; ++i)
-      stride[i] = base::checked_cast<int>(
-          gfx::RowSizeForBufferFormat(size_.width(), format_, i));
+  int stride(size_t plane) const override {
+    DCHECK_LT(plane, gfx::NumberOfPlanesForBufferFormat(format_));
+    return base::checked_cast<int>(gfx::RowSizeForBufferFormat(
+        size_.width(), format_, static_cast<int>(plane)));
   }
   gfx::GpuMemoryBufferId GetId() const override {
     NOTREACHED();