Don't paint throttled FrameView

This avoids crash on unexpected null TotalPropertyTreeStateForContents()
in https://chromium-review.googlesource.com/c/chromium/src/+/786130
for SPv175/non-RootLayerScrolling. This is separated from that CL which
is a pure SPv175 refactor.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I5ad8db400838f4e9a5a5f87847e62858c6460759
Reviewed-on: https://chromium-review.googlesource.com/791935
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519486}

third_party/WebKit/Source/core/paint/FramePainter.cpp

@@ -33,6 +33,9 @@ bool FramePainter::in_paint_contents_ = false;
 void FramePainter::Paint(GraphicsContext& context,
                          const GlobalPaintFlags global_paint_flags,
                          const CullRect& rect) {
+  if (GetFrameView().ShouldThrottleRendering())
+    return;
+
   GetFrameView().NotifyPageThatContentAreaWillPaint();
 
   IntRect document_dirty_rect;

third_party/WebKit/Source/core/paint/ViewPainter.cpp

@@ -32,9 +32,7 @@ void ViewPainter::Paint(const PaintInfo& paint_info,
   DCHECK(LayoutPoint(IntPoint(paint_offset.X().ToInt(),
                               paint_offset.Y().ToInt())) == paint_offset);
 
-  const LocalFrameView* frame_view = layout_view_.GetFrameView();
-  if (frame_view->ShouldThrottleRendering())
-    return;
+  DCHECK(!layout_view_.GetFrameView()->ShouldThrottleRendering());
 
   layout_view_.PaintObject(paint_info, paint_offset);
   BlockPainter(layout_view_)