services/ui: Use the correct offset and stride in MojoGpuMemoryBuffer.

services/ui/public/cpp/mojo_gpu_memory_buffer.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/public/cpp/mojo_gpu_memory_buffer.h"
 
 #include <stdint.h>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/shared_memory.h"
 #include "base/numerics/safe_conversions.h"
 #include "build/build_config.h"
 #include "mojo/public/cpp/system/buffer.h"
 #include "mojo/public/cpp/system/platform_handle.h"
 #include "ui/gfx/buffer_format_util.h"
 
 namespace ui {
 
 MojoGpuMemoryBufferImpl::MojoGpuMemoryBufferImpl(
     const gfx::Size& size,
     gfx::BufferFormat format,
-    std::unique_ptr<base::SharedMemory> shared_memory)
+    std::unique_ptr<base::SharedMemory> shared_memory,
+    size_t offset,
+    int stride)
     : GpuMemoryBufferImpl(gfx::GenericSharedMemoryId(0), size, format),
-      shared_memory_(std::move(shared_memory)) {}
+      shared_memory_(std::move(shared_memory)),
+      offset_(offset),
+      stride_(stride) {}
 
 // TODO(rjkroege): Support running a destructor callback as necessary.
 MojoGpuMemoryBufferImpl::~MojoGpuMemoryBufferImpl() {}
 
 // static
 std::unique_ptr<gfx::GpuMemoryBuffer> MojoGpuMemoryBufferImpl::Create(
     const gfx::Size& size,
     gfx::BufferFormat format,
     gfx::BufferUsage usage) {
   size_t bytes = gfx::BufferSizeForBufferFormat(size, format);
 
   mojo::ScopedSharedBufferHandle handle =
       mojo::SharedBufferHandle::Create(bytes);
   if (!handle.is_valid())
     return nullptr;
 
   base::SharedMemoryHandle platform_handle;
   size_t shared_memory_size;
   bool readonly;
   MojoResult result = mojo::UnwrapSharedMemoryHandle(
       std::move(handle), &platform_handle, &shared_memory_size, &readonly);
   if (result != MOJO_RESULT_OK)
     return nullptr;
   DCHECK_EQ(shared_memory_size, bytes);
 
   auto shared_memory =
       base::MakeUnique<base::SharedMemory>(platform_handle, readonly);
-  return base::MakeUnique<MojoGpuMemoryBufferImpl>(
-      size, format, std::move(shared_memory));
+  const int stride = base::checked_cast<int>(
+      gfx::RowSizeForBufferFormat(size.width(), format, 0));
+  return base::WrapUnique(new MojoGpuMemoryBufferImpl(
+      size, format, std::move(shared_memory), 0, stride));
 }
 
 // static
 std::unique_ptr<gfx::GpuMemoryBuffer> MojoGpuMemoryBufferImpl::CreateFromHandle(
     const gfx::GpuMemoryBufferHandle& handle,
     const gfx::Size& size,
     gfx::BufferFormat format,
     gfx::BufferUsage usage) {
   DCHECK_EQ(handle.type, gfx::SHARED_MEMORY_BUFFER);
   DCHECK(base::SharedMemory::IsHandleValid(handle.handle));
   const bool readonly = false;
   auto shared_memory =
       base::MakeUnique<base::SharedMemory>(handle.handle, readonly);
-  return base::MakeUnique<MojoGpuMemoryBufferImpl>(
-      size, format, std::move(shared_memory));
+  return base::WrapUnique(new MojoGpuMemoryBufferImpl(
+      size, format, std::move(shared_memory), handle.offset, handle.stride));
 }
 
 MojoGpuMemoryBufferImpl* MojoGpuMemoryBufferImpl::FromClientBuffer(
     ClientBuffer buffer) {
   return reinterpret_cast<MojoGpuMemoryBufferImpl*>(buffer);
 }
 
 const unsigned char* MojoGpuMemoryBufferImpl::GetMemory() const {
   return static_cast<const unsigned char*>(shared_memory_->memory());
 }
 
 bool MojoGpuMemoryBufferImpl::Map() {
   DCHECK(!mapped_);
-  if (!shared_memory_->Map(gfx::BufferSizeForBufferFormat(size_, format_)))
+  DCHECK_EQ(static_cast<size_t>(stride_),
+            gfx::RowSizeForBufferFormat(size_.width(), format_, 0));
+  const size_t buffer_size = gfx::BufferSizeForBufferFormat(size_, format_);
+  const size_t map_size = offset_ + buffer_size;
+  if (!shared_memory_->Map(map_size))
     return false;
   mapped_ = true;
   return true;
 }
 
 void* MojoGpuMemoryBufferImpl::memory(size_t plane) {
   DCHECK(mapped_);
   DCHECK_LT(plane, gfx::NumberOfPlanesForBufferFormat(format_));
-  return reinterpret_cast<uint8_t*>(shared_memory_->memory()) +
+  return reinterpret_cast<uint8_t*>(shared_memory_->memory()) + offset_ +
          gfx::BufferOffsetForBufferFormat(size_, format_, plane);
 }
 
 void MojoGpuMemoryBufferImpl::Unmap() {
   DCHECK(mapped_);
   shared_memory_->Unmap();
   mapped_ = false;
 }
 
 int MojoGpuMemoryBufferImpl::stride(size_t plane) const {
   DCHECK_LT(plane, gfx::NumberOfPlanesForBufferFormat(format_));
   return base::checked_cast<int>(gfx::RowSizeForBufferFormat(
       size_.width(), format_, static_cast<int>(plane)));
 }
 
 gfx::GpuMemoryBufferHandle MojoGpuMemoryBufferImpl::GetHandle() const {
   gfx::GpuMemoryBufferHandle handle;
   handle.type = gfx::SHARED_MEMORY_BUFFER;
   handle.handle = shared_memory_->handle();
-  handle.offset = 0;
-  handle.stride = static_cast<int32_t>(
-      gfx::RowSizeForBufferFormat(size_.width(), format_, 0));
+  handle.offset = offset_;
+  handle.stride = stride_;
 
   return handle;
 }
 
 gfx::GpuMemoryBufferType MojoGpuMemoryBufferImpl::GetBufferType() const {
   return gfx::SHARED_MEMORY_BUFFER;
 }
 
 }  // namespace ui