Avoid element id collisions with the visual viewport

third_party/WebKit/Source/web/tests/VisualViewportTest.cpp

Index: third_party/WebKit/Source/web/tests/VisualViewportTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/VisualViewportTest.cpp b/third_party/WebKit/Source/web/tests/VisualViewportTest.cpp
index 6a06e377bfc6ef12e09ece72292c01455913fcd9..bc13e0e953f69508421c68c6f1252264f8686b08 100644
--- a/third_party/WebKit/Source/web/tests/VisualViewportTest.cpp
+++ b/third_party/WebKit/Source/web/tests/VisualViewportTest.cpp
@@ -19,6 +19,7 @@
 #include "platform/PlatformGestureEvent.h"
 #include "platform/geometry/DoublePoint.h"
 #include "platform/geometry/DoubleRect.h"
+#include "platform/graphics/CompositorElementId.h"
 #include "platform/testing/RuntimeEnabledFeaturesTestHelpers.h"
 #include "platform/testing/URLTestHelpers.h"
 #include "public/platform/Platform.h"
@@ -783,6 +784,9 @@ TEST_P(ParameterizedVisualViewportTest,
   // Ensure the scroll layer matches the frame view's size.
   EXPECT_SIZE_EQ(FloatSize(320, 240), visualViewport.scrollLayer()->size());
 
+  EXPECT_EQ(static_cast<int>(CompositorSubElementId::Viewport),
+            visualViewport.scrollLayer()->elementId().secondaryId);
+
   // Ensure the location and scale were reset.
   EXPECT_SIZE_EQ(FloatSize(), visualViewport.scrollOffset());
   EXPECT_EQ(1, visualViewport.scale());