Remove unused clip field

Been unused for years.

Change-Id: Icc6c9a668016da2d82ae6f377a9499554bb3341e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2127887Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754747}

content/common/input/sync_compositor_messages.h

@@ -31,7 +31,6 @@ struct SyncCompositorDemandDrawHwParams {
   ~SyncCompositorDemandDrawHwParams();
 
   gfx::Size viewport_size;
-  gfx::Rect clip;
   gfx::Rect viewport_rect_for_tile_priority;
   gfx::Transform transform_for_tile_priority;
 };