Fix for pinch virtual viewport flag wasn't fully enabled.

content/browser/gpu/compositor_util.h

Index: content/browser/gpu/compositor_util.h
diff --git a/content/browser/gpu/compositor_util.h b/content/browser/gpu/compositor_util.h
index b3cf2045a9cb484856aa434c75d2f9e4edc1d356..72a3ac0d42dda9a943a147d77cef82b6cbbc0c24 100644
--- a/content/browser/gpu/compositor_util.h
+++ b/content/browser/gpu/compositor_util.h
@@ -13,6 +13,10 @@ namespace content {
 // Note: When adding a function here, please make sure the logic is not
 // duplicated in the renderer.
 
+// Returns true if the virtual viewport model of pinch-to-zoom is on (via
+// flags, or platform default).
+CONTENT_EXPORT bool IsPinchVirtualViewportEnabled();
+
 // Returns true if the threaded compositor is on (via flags or field trial).
 CONTENT_EXPORT bool IsThreadedCompositingEnabled();