[PE] Remove GetDocument() calls from a frequently used PaintInvalidator func.

This patch removes GetDocument() call which loads a large object into
memory for every PaintInvalidator::InvalidatePaint call on a LayoutObject.

Instead, it stores this value on the paint invalidator and updates it
whwnever we encounter a new LocalFrameView during the prepaint walk.

On small dom / small invalidation this only has a small benefit, but
for complicated dom, my local perf tests show large improvements.

R=chrishtr@chromium.org

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I51139b8f8a802d608b583656d0be8bd2b7f13022
Reviewed-on: https://chromium-review.googlesource.com/924277Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537414}

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

@@ -557,8 +557,7 @@ void PaintInvalidator::InvalidatePaint(
 
   UpdatePaintingLayer(object, context);
 
-  if (object.GetDocument().Printing() &&
-      !RuntimeEnabledFeatures::PrintBrowserEnabled())
+  if (document_printing_ && !RuntimeEnabledFeatures::PrintBrowserEnabled())
     return;  // Don't invalidate paints if we're printing.
 
   // TODO(chrishtr): refactor to remove these slow paths by expanding their

third_party/WebKit/Source/core/paint/PaintInvalidator.h

@@ -153,6 +153,7 @@ class PaintInvalidator {
 
  private:
   friend struct PaintInvalidatorContext;
+  friend class PrePaintTreeWalk;
   template <typename Rect, typename Point>
   static LayoutRect MapLocalRectToVisualRectInBacking(
       const LayoutObject&,
@@ -175,6 +176,7 @@ class PaintInvalidator {
                                       PaintInvalidatorContext&);
 
   Vector<const LayoutObject*> pending_delayed_paint_invalidations_;
+  bool document_printing_ = false;
 };
 
 }  // namespace blink

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

@@ -15,6 +15,7 @@
 #include "core/paint/compositing/CompositingLayerPropertyUpdater.h"
 #include "core/paint/ng/ng_paint_fragment.h"
 #include "platform/graphics/paint/GeometryMapper.h"
+#include "platform/wtf/AutoReset.h"
 
 namespace blink {
 
@@ -88,6 +89,9 @@ void PrePaintTreeWalk::Walk(LocalFrameView& frame_view) {
   auto context = [this]() -> PrePaintTreeWalkContext& {
     return context_storage_.back();
   };
+  AutoReset<bool> printing_reset(
+      &paint_invalidator_.document_printing_,
+      frame_view.GetFrame().GetDocument()->Printing());
 
   // ancestorOverflowLayer does not cross frame boundaries.
   context().ancestor_overflow_paint_layer = nullptr;