Add a flag to allow renderer to use software compositor when GL compositor doesn't work.

cc/layers/texture_layer_unittest.cc

Index: cc/layers/texture_layer_unittest.cc
diff --git a/cc/layers/texture_layer_unittest.cc b/cc/layers/texture_layer_unittest.cc
index 1c07e825e5f4e1e8577a5c2a1835af048bd4c6db..aa08e9f81ee9a854af56afa1ae2527637dd25656 100644
--- a/cc/layers/texture_layer_unittest.cc
+++ b/cc/layers/texture_layer_unittest.cc
@@ -793,7 +793,8 @@ class TextureLayerClientTest
         expected_used_textures_on_draw_(0),
         expected_used_textures_on_commit_(0) {}
 
-  virtual scoped_ptr<OutputSurface> CreateOutputSurface() OVERRIDE {
+  virtual scoped_ptr<OutputSurface> CreateOutputSurface(bool fallback)
+      OVERRIDE {
     scoped_ptr<TestWebGraphicsContext3D> context(
         TestWebGraphicsContext3D::Create());
     context_ = context.get();
@@ -907,7 +908,8 @@ class TextureLayerLostContextTest
       : texture_(0),
         draw_count_(0) {}
 
-  virtual scoped_ptr<OutputSurface> CreateOutputSurface() OVERRIDE {
+  virtual scoped_ptr<OutputSurface> CreateOutputSurface(bool fallback)
+      OVERRIDE {
     texture_context_ = TestWebGraphicsContext3D::Create();
     texture_ = texture_context_->createTexture();
     return CreateFakeOutputSurface();