Change switches::kContentImageTextureTarget to a list of image texture targets

Not knowing the GpuMemoryBuffer format that the compostor will use, the host is
hard to determine the image texture target properly. This CL changes
switches::kContentImageTextureTarget to a list of targets for each format, so
that the compositor can decide what format it wants to use without having to
worry about the target being wrong.

BUG=490362,512665

CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1251693003

Cr-Commit-Position: refs/heads/master@{#342339}
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index eb6516e..c7aeb9f 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -195,7 +195,7 @@
   bool IsZeroCopyEnabled() override;
   bool IsOneCopyEnabled() override;
   bool IsElasticOverscrollEnabled() override;
-  uint32 GetImageTextureTarget() override;
+  std::vector<unsigned> GetImageTextureTargets() override;
   scoped_refptr<base::SingleThreadTaskRunner>
   GetCompositorMainThreadTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner>
@@ -615,7 +615,7 @@
   bool is_zero_copy_enabled_;
   bool is_one_copy_enabled_;
   bool is_elastic_overscroll_enabled_;
-  unsigned use_image_texture_target_;
+  std::vector<unsigned> use_image_texture_targets_;
   bool is_gather_pixel_refs_enabled_;
 
   class PendingRenderFrameConnect