Clamp YUV videos to their visible size in the shader

cc/layers/video_layer_impl.cc

Index: cc/layers/video_layer_impl.cc
diff --git a/cc/layers/video_layer_impl.cc b/cc/layers/video_layer_impl.cc
index 5f18a768ca4dcf0c4b72767843ef7dc31eeccebc..0c43fe9396097cf5ee319eba3ffe5cc90935be98 100644
--- a/cc/layers/video_layer_impl.cc
+++ b/cc/layers/video_layer_impl.cc
@@ -188,6 +188,13 @@ void VideoLayerImpl::AppendQuads(RenderPass* render_pass,
   const float tex_y_offset =
       static_cast<float>(visible_rect.y()) / coded_size.height();
 
+  // Vertex shader should clamp to the visible rect, and then minus
+  // half a pixel (of the coded size) to account for bilinear filtering.
+  // This prevents sampling outside of the visible rect.
+  gfx::SizeF half_pixel(0.5f / coded_size.width(), 0.5f / coded_size.height());
+  gfx::SizeF clamp_size(tex_width_scale + tex_x_offset - half_pixel.width(),
+                        tex_height_scale + tex_y_offset - half_pixel.height());
+
   switch (frame_resource_type_) {
     // TODO(danakj): Remove this, hide it in the hardware path.
     case VideoFrameExternalResources::SOFTWARE_RESOURCE: {
@@ -230,16 +237,10 @@ void VideoLayerImpl::AppendQuads(RenderPass* render_pass,
       YUVVideoDrawQuad* yuv_video_quad =
           render_pass->CreateAndAppendDrawQuad<YUVVideoDrawQuad>();
       yuv_video_quad->SetNew(
-          shared_quad_state,
-          quad_rect,
-          opaque_rect,
-          visible_quad_rect,
-          tex_coord_rect,
-          frame_resources_[0],
-          frame_resources_[1],
+          shared_quad_state, quad_rect, opaque_rect, visible_quad_rect,
+          tex_coord_rect, clamp_size, frame_resources_[0], frame_resources_[1],
           frame_resources_[2],
-          frame_resources_.size() > 3 ? frame_resources_[3] : 0,
-          color_space);
+          frame_resources_.size() > 3 ? frame_resources_[3] : 0, color_space);
       break;
     }
     case VideoFrameExternalResources::RGB_RESOURCE: {