Spurious scrollbars should not be drawn when overflow is applied to a frame.

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp b/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
index cabca2c1c9c6e0f596ff47b762509922b00891f9..852fc37ff6f7f86c44c403783528e4558f289414 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp
@@ -349,6 +349,13 @@ void StyleAdjuster::adjustStyleForHTMLElement(ComputedStyle& style, const Comput
         return;
     }
 
+    if (isHTMLFrameElementBase(element)) {
+        // Frames cannot overflow (they are always the size we ask them to be).
+        // Some compositing code paths may try to draw scrollbars anyhow.
+        style.setOverflowX(OverflowVisible);
+        style.setOverflowY(OverflowVisible);

[leviw_travelin_and_unemployed, 2016/03/29 18:40:42]

Early return?

+    }
+
     if (isHTMLRTElement(element)) {
         // Ruby text does not support float or position. This might change with evolution of the specification.
         style.setPosition(StaticPosition);