Defer compositor context creation to the thread.

cc/output/context_provider.h

 // Copyright (c) 2013 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.
 
 #ifndef CC_OUTPUT_CONTEXT_PROVIDER_H_
 #define CC_OUTPUT_CONTEXT_PROVIDER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 39 matching lines @@
 
     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
-  // from the same thread unless the function has some explicitly specified
-  // rules for access on a different thread. See SetupLockOnMainThread(), which
-  // can be used to provide access from multiple threads.
-  virtual bool BindToCurrentThread() = 0;
+  // This Factory API is how to create a context provider in a deferred way (ie.
+  // on another thread than the main thread).
+  class DeferredCreate {

[piman, 2016/05/17 03:41:40]

naming-wise, how about Factory? It's shorter, and I think it carries the right
idea?

[danakj, 2016/05/17 19:53:32]

Ya it does. I was like ContextProvider::Factory is very close to
ContextProvider::Provider, but whatever, embrace it I guess.

+   public:
+    // Creates and returns a new context provider. The context provider may only
+    // be used on the thread it is created on unless it supports locking (via
+    // the ScopedContextLock class).
+    virtual scoped_refptr<ContextProvider> CreateContext() = 0;
+
+   protected:
+    DeferredCreate() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(DeferredCreate);
+  };
 
   virtual gpu::gles2::GLES2Interface* ContextGL() = 0;
   virtual gpu::ContextSupport* ContextSupport() = 0;
   virtual class GrContext* GrContext() = 0;
 
   // Invalidates the cached OpenGL state in GrContext.
   // See skia GrContext::resetContext for details.
   virtual void InvalidateGrContext(uint32_t state) = 0;
 
   // Returns the capabilities of the currently bound 3d context.
@@ skipping 20 matching lines @@
   virtual base::Lock* GetLock() = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<ContextProvider>;
   virtual ~ContextProvider() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_CONTEXT_PROVIDER_H_