Disable partial swaps for webview guest renderer until we can figure out how to do that properly.

content/common/gpu/texture_image_transport_surface.cc

Index: content/common/gpu/texture_image_transport_surface.cc
diff --git a/content/common/gpu/texture_image_transport_surface.cc b/content/common/gpu/texture_image_transport_surface.cc
index a40b60df36e7bc9c505f4483869a54e395342d41..ea05e4aa58f2648953e5e061cebfa3223d31344d 100644
--- a/content/common/gpu/texture_image_transport_surface.cc
+++ b/content/common/gpu/texture_image_transport_surface.cc
@@ -278,7 +278,8 @@ std::string TextureImageTransportSurface::GetExtensions() {
   std::string extensions = gfx::GLSurface::GetExtensions();
   extensions += extensions.empty() ? "" : " ";
   extensions += "GL_CHROMIUM_front_buffer_cached ";
-  extensions += "GL_CHROMIUM_post_sub_buffer";
+  if (handle_.transport_type != gfx::TEXTURE_TRANSPORT_NO_PARTIAL_SWAP)
+    extensions += "GL_CHROMIUM_post_sub_buffer";
   return extensions;
 }