Deflake VisualPropertiesPropagation_RootWindowSegments

Instead of looping for the expected condition, use the LocalSurfaceId
increasing as evidence that the expected visual properties update was
delivered, and test for the expected values directly. If the test
remains flaky, this will give a better indication of where things are
breaking down.

Also fix the math for the expected width of the second segment - for
devices where there are an odd number of DIPs in width, the segments
won't be equal.

R=jonross@chromium.org

Bug: 1089994
Change-Id: I1a81dc73055a4fca8ffc4b577b1b25046dcf23d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2433306
Commit-Queue: Daniel Libby <dlibby@microsoft.com>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811550}

content/browser/renderer_host/render_widget_host_view_child_frame_browsertest.cc

@@ -538,9 +538,28 @@ IN_PROC_BROWSER_TEST_F(RenderWidgetHostViewChildFrameBrowserTest,
   std::vector<gfx::Rect> expected_segments;
   expected_segments.emplace_back(0, 0, emulated_display_feature.offset,
                                  root_view_size.height());
-  expected_segments.emplace_back(
-      emulated_display_feature.offset + emulated_display_feature.mask_length, 0,
-      emulated_display_feature.offset, root_view_size.height());
+  const int second_segment_offset =
+      emulated_display_feature.offset + emulated_display_feature.mask_length;
+  expected_segments.emplace_back(second_segment_offset, 0,
+                                 root_view_size.width() - second_segment_offset,
+                                 root_view_size.height());
+
+  base::Optional<blink::VisualProperties> properties =
+      oopchild->current_frame_host()
+          ->GetRenderWidgetHost()
+          ->GetLastVisualPropertiesSentToRendererForTesting();
+  EXPECT_TRUE(properties);
+  EXPECT_TRUE(properties->local_surface_id);
+  viz::LocalSurfaceId oopchild_initial_lsid =
+      properties->local_surface_id.value();
+
+  properties = oopdescendant->current_frame_host()
+                   ->GetRenderWidgetHost()
+                   ->GetLastVisualPropertiesSentToRendererForTesting();
+  EXPECT_TRUE(properties);
+  EXPECT_TRUE(properties->local_surface_id);
+  viz::LocalSurfaceId oopdescendant_initial_lsid =
+      properties->local_surface_id.value();
 
   {
     // Watch for visual properties changes, first to the child oop-iframe, then
@@ -555,9 +574,11 @@ IN_PROC_BROWSER_TEST_F(RenderWidgetHostViewChildFrameBrowserTest,
           oopchild->current_frame_host()
               ->GetRenderWidgetHost()
               ->GetLastVisualPropertiesSentToRendererForTesting();
-      if (properties &&
-          properties->root_widget_window_segments == expected_segments)
+      if (properties && properties->local_surface_id &&
+          oopchild_initial_lsid < properties->local_surface_id) {
+        EXPECT_EQ(properties->root_widget_window_segments, expected_segments);
         break;
+      }
       base::RunLoop().RunUntilIdle();
     }
     while (true) {
@@ -565,9 +586,11 @@ IN_PROC_BROWSER_TEST_F(RenderWidgetHostViewChildFrameBrowserTest,
           oopdescendant->current_frame_host()
               ->GetRenderWidgetHost()
               ->GetLastVisualPropertiesSentToRendererForTesting();
-      if (properties &&
-          properties->root_widget_window_segments == expected_segments)
+      if (properties && properties->local_surface_id &&
+          oopdescendant_initial_lsid < properties->local_surface_id) {
+        EXPECT_EQ(properties->root_widget_window_segments, expected_segments);
         break;
+      }
       base::RunLoop().RunUntilIdle();
     }
   }