cc: Partial tile update for one-copy raster.

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index db1b35eb0ccaadeaa428bd4540771b2cc1f71e91..1c0b554a4e8861dd4b29d7eeae119cfd6c7d4ba5 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -1088,16 +1088,17 @@ ResourceProvider::ScopedWriteLockGpuMemoryBuffer::
   resource_->read_lock_fences_enabled = true;
 }
 
-gfx::GpuMemoryBuffer*
-ResourceProvider::ScopedWriteLockGpuMemoryBuffer::GetGpuMemoryBuffer() {
-  if (!gpu_memory_buffer_) {
-    scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer =
-        gpu_memory_buffer_manager_->AllocateGpuMemoryBuffer(
-            size_, ToGpuMemoryBufferFormat(format_), gfx::GpuMemoryBuffer::MAP);
-    gpu_memory_buffer_ = gpu_memory_buffer.release();
-  }
-
-  return gpu_memory_buffer_;
+bool ResourceProvider::ScopedWriteLockGpuMemoryBuffer::AllocateGpuMemoryBuffer(
+    bool persistent) {
+  DCHECK(!gpu_memory_buffer_);
+  gfx::GpuMemoryBuffer::Usage usage = persistent
+                                          ? gfx::GpuMemoryBuffer::PERSISTENT_MAP
+                                          : gfx::GpuMemoryBuffer::MAP;
+  scoped_ptr<gfx::GpuMemoryBuffer> gpu_memory_buffer =
+      gpu_memory_buffer_manager_->AllocateGpuMemoryBuffer(
+          size_, ToGpuMemoryBufferFormat(format_), usage);
+  gpu_memory_buffer_ = gpu_memory_buffer.release();
+  return !!gpu_memory_buffer_;
 }
 
 ResourceProvider::ScopedWriteLockGr::ScopedWriteLockGr(