Defer compositor context creation to the thread.

cc/test/test_web_graphics_context_3d.cc

Index: cc/test/test_web_graphics_context_3d.cc
diff --git a/cc/test/test_web_graphics_context_3d.cc b/cc/test/test_web_graphics_context_3d.cc
index 2641c9011d75132b7298529a8d2be44f39350a22..cc447c2e58b1b8c7dedb2fa7ffe0d59e8abf577c 100644
--- a/cc/test/test_web_graphics_context_3d.cc
+++ b/cc/test/test_web_graphics_context_3d.cc
@@ -73,7 +73,7 @@ TestWebGraphicsContext3D::TestWebGraphicsContext3D()
       bound_buffer_(0),
       weak_ptr_factory_(this) {
   CreateNamespace();
-  set_support_image(true);
+  test_capabilities_.image = true;
 }
 
 TestWebGraphicsContext3D::~TestWebGraphicsContext3D() {
@@ -762,10 +762,6 @@ void TestWebGraphicsContext3D::RetireRenderbufferId(GLuint id) {
   namespace_->renderbuffer_set.erase(id);
 }
 
-void TestWebGraphicsContext3D::SetMaxSamples(int max_samples) {
-  test_capabilities_.max_samples = max_samples;
-}
-
 TestWebGraphicsContext3D::TextureTargets::TextureTargets() {
   // Initialize default bindings.
   bound_textures_[GL_TEXTURE_2D] = 0;