Compute damage rect for Cast video compositing

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 71861fb361d8b7dac8789e2fa311af09b4f014d7..c32ab20fdbc2267f3af0dd09ba3d6af97ea0f132 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -401,6 +401,7 @@ GLRenderer::GLRenderer(const RendererSettings* settings,
   use_blend_equation_advanced_ = context_caps.blend_equation_advanced;
   use_blend_equation_advanced_coherent_ =
       context_caps.blend_equation_advanced_coherent;
+  use_swap_with_damage_ = context_caps.swap_buffers_with_damage;
 
   InitializeSharedObjects();
 }
@@ -2905,6 +2906,7 @@ void GLRenderer::SwapBuffers(std::vector<ui::LatencyInfo> latency_info) {
   OutputSurfaceFrame output_frame;
   output_frame.latency_info = std::move(latency_info);
   output_frame.size = surface_size;
+  output_frame.swap_with_damage_rect = gfx::Rect(surface_size);
   if (use_partial_swap_) {
     // If supported, we can save significant bandwidth by only swapping the
     // damaged/scissored region (clamped to the viewport).
@@ -2926,6 +2928,13 @@ void GLRenderer::SwapBuffers(std::vector<ui::LatencyInfo> latency_info) {
     output_frame.sub_buffer_rect = swap_buffer_rect_;
   }
 
+  if (use_swap_with_damage_) {
+    gfx::Rect swap_with_damage_rect;
+    if (overlay_processor_->GetSwapWithDamageRect(&swap_with_damage_rect)) {
+      output_frame.swap_with_damage_rect = swap_with_damage_rect;
+    }
+  }
+
   swapping_overlay_resources_.push_back(std::move(pending_overlay_resources_));
   pending_overlay_resources_.clear();