Revert of Re-land: cc: Use worker context for one-copy tile initialization. (patchset #29 id:560001 of https://codereview.chromium.org/1230203007/ )

Reason for revert:
Sorry Dave. I'm reverting as this broke mandoline. To see the breakage build mandoline:all, and run with:
mandoline --oopif-always-create-new-frame-tree http://phuang.github.io/iframe.html .

We do have mandoline tests that run, but they run with the code path  gfx::GLSurfaceTestSupport::InitializeOneOff(), which is why they likely still pass. I'll see about making the tests not run with that config.

Original issue's description:
> Re-land: cc: Use worker context for one-copy tile initialization.
>
> This moves management of staging resources to
> OneCopyTileTaskWorkerPool class. This makes it possible
> to use a worker context to issue and detect when copy
> operations complete.
>
> BUG=490295
> TBR=jamesr@chromium.org, sky@chromium.org
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/af0ab609b53c64ce43172be42e20e7ca8beab497
> Cr-Commit-Position: refs/heads/master@{#343947}

TBR=jamesr@chromium.org,kbr@chromium.org,piman@chromium.org,primiano@chromium.org,vmiura@chromium.org,vmpstr@chromium.org,reveman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=490295

Review URL: https://codereview.chromium.org/1298143003

Cr-Commit-Position: refs/heads/master@{#344042}

1 files changed, 0 insertions, 22 deletions

diff --git a/cc/output/context_provider.h b/cc/output/context_provider.h
index c024e02..aa4367d 100644
--- a/cc/output/context_provider.h
+++ b/cc/output/context_provider.h
@@ -7,7 +7,6 @@
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
-#include "base/synchronization/lock.h"
 #include "cc/base/cc_export.h"
 #include "gpu/command_buffer/common/capabilities.h"
 
@@ -27,27 +26,6 @@ struct ManagedMemoryPolicy;
 
 class ContextProvider : public base::RefCountedThreadSafe<ContextProvider> {
  public:
-  class ScopedContextLock {
-   public:
-    explicit ScopedContextLock(ContextProvider* context_provider)
-        : context_provider_(context_provider),
-          context_lock_(*context_provider_->GetLock()) {
-      // Allow current thread to bind to |context_provider|.
-      context_provider_->DetachFromThread();
-    }
-    ~ScopedContextLock() {
-      // Allow a different thread to bind to |context_provider|.
-      context_provider_->DetachFromThread();
-    }
-
-    gpu::gles2::GLES2Interface* ContextGL() {
-      return context_provider_->ContextGL();
-    }
-
-   private:
-    ContextProvider* const context_provider_;
-    base::AutoLock context_lock_;
-  };
   // Bind the 3d context to the current thread. This should be called before
   // accessing the contexts. Calling it more than once should have no effect.
   // Once this function has been called, the class should only be accessed