Remove the concept of OutputSurface from ResourceProvider.

cc/raster/staging_buffer_pool.cc

Index: cc/raster/staging_buffer_pool.cc
diff --git a/cc/raster/staging_buffer_pool.cc b/cc/raster/staging_buffer_pool.cc
index cb14f8224ba83db03c468ee26c9ccb7ba790da68..99fb43843105ece60a3ac000cbd3236ce601c003 100644
--- a/cc/raster/staging_buffer_pool.cc
+++ b/cc/raster/staging_buffer_pool.cc
@@ -120,22 +120,13 @@ void StagingBuffer::OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd,
   pmd->AddOwnershipEdge(buffer_dump->guid(), shared_buffer_guid, kImportance);
 }
 
-// static
-std::unique_ptr<StagingBufferPool> StagingBufferPool::Create(
-    base::SequencedTaskRunner* task_runner,
-    ResourceProvider* resource_provider,
-    bool use_partial_raster,
-    int max_staging_buffer_usage_in_bytes) {
-  return base::WrapUnique(
-      new StagingBufferPool(task_runner, resource_provider, use_partial_raster,
-                            max_staging_buffer_usage_in_bytes));
-}
-
 StagingBufferPool::StagingBufferPool(base::SequencedTaskRunner* task_runner,
+                                     ContextProvider* worker_context_provider,
                                      ResourceProvider* resource_provider,
                                      bool use_partial_raster,
                                      int max_staging_buffer_usage_in_bytes)
     : task_runner_(task_runner),
+      worker_context_provider_(worker_context_provider),
       resource_provider_(resource_provider),
       use_partial_raster_(use_partial_raster),
       max_staging_buffer_usage_in_bytes_(max_staging_buffer_usage_in_bytes),
@@ -145,6 +136,7 @@ StagingBufferPool::StagingBufferPool(base::SequencedTaskRunner* task_runner,
           base::TimeDelta::FromMilliseconds(kStagingBufferExpirationDelayMs)),
       reduce_memory_usage_pending_(false),
       weak_ptr_factory_(this) {
+  DCHECK(worker_context_provider_);
   base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       this, "cc::StagingBufferPool", base::ThreadTaskRunnerHandle::Get());
   reduce_memory_usage_callback_ = base::Bind(
@@ -243,11 +235,7 @@ std::unique_ptr<StagingBuffer> StagingBufferPool::AcquireStagingBuffer(
 
   std::unique_ptr<StagingBuffer> staging_buffer;
 
-  ContextProvider* context_provider =
-      resource_provider_->output_surface()->worker_context_provider();
-  DCHECK(context_provider);
-
-  ContextProvider::ScopedContextLock scoped_context(context_provider);
+  ContextProvider::ScopedContextLock scoped_context(worker_context_provider_);
 
   gpu::gles2::GLES2Interface* gl = scoped_context.ContextGL();
   DCHECK(gl);
@@ -392,12 +380,8 @@ void StagingBufferPool::ReduceMemoryUsage() {
 void StagingBufferPool::ReleaseBuffersNotUsedSince(base::TimeTicks time) {
   lock_.AssertAcquired();
 
-  ContextProvider* context_provider =
-      resource_provider_->output_surface()->worker_context_provider();
-  DCHECK(context_provider);
-
   {
-    ContextProvider::ScopedContextLock scoped_context(context_provider);
+    ContextProvider::ScopedContextLock scoped_context(worker_context_provider_);
 
     gpu::gles2::GLES2Interface* gl = scoped_context.ContextGL();
     DCHECK(gl);