Move CalculateScrollbarModes from FrameView to LayoutView.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index adffb22d30e612c6b4f40fb2974165c5907178f7..12f2e12b23ee2a8b682feb3c359b156cf580960b 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -666,18 +666,13 @@ bool PaintLayerScrollableArea::UserInputScrollable(
     return true;
 
   if (Box().IsLayoutView()) {

[szager1, 2017/05/22 18:29:35]

General observation: we should probably work towards eliminating calls to
Box().IsLayoutView(), and instead delegate to virtual methods defined on
LayoutBox.  UserInputScrollable is a good candidate, because its logic doesn't
use any information from PLSA, it's all from Box().

No need to do anything for this patch, just a suggestion going forward.

[skobes, 2017/05/22 19:15:10]

Agreed.  Scrollability is a big mess right now with lots of near redundancy and
similar-sounding methods that do different things.  I initially thought of
making CalculateScrollbarModes virtual on LayoutBox, but in that case it should
probably take on the rest of the logic currently in
PLSA::ComputeScrollbarExistence and replace other LayoutBox APIs like
ScrollsOverflow{X,Y} and HasAuto{Horizontal,Vertical}Scrollbar... it was looking
like a huge ball of yarn to untangle so I backed off from that idea.  Would be
nice to clean it all up somehow.

-    if (LocalFrame* frame = Box().GetFrame()) {
-      if (FrameView* frame_view = frame->View()) {
-        ScrollbarMode h_mode;
-        ScrollbarMode v_mode;
-        frame_view->CalculateScrollbarModes(h_mode, v_mode);
-        if (orientation == kHorizontalScrollbar &&
-            h_mode == kScrollbarAlwaysOff)
-          return false;
-        if (orientation == kVerticalScrollbar && v_mode == kScrollbarAlwaysOff)
-          return false;
-      }
-    }
+    ScrollbarMode h_mode;
+    ScrollbarMode v_mode;
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
+    if (orientation == kHorizontalScrollbar && h_mode == kScrollbarAlwaysOff)
+      return false;
+    if (orientation == kVerticalScrollbar && v_mode == kScrollbarAlwaysOff)
+      return false;
   }
 
   EOverflow overflow_style = (orientation == kHorizontalScrollbar)
@@ -1291,21 +1286,17 @@ void PaintLayerScrollableArea::ComputeScrollbarExistence(
   // values, due to which we are destroying the scrollbars that were already
   // present.
   if (Box().IsLayoutView()) {
-    if (LocalFrame* frame = Box().GetFrame()) {
-      if (FrameView* frame_view = frame->View()) {
-        ScrollbarMode h_mode;
-        ScrollbarMode v_mode;
-        frame_view->CalculateScrollbarModes(h_mode, v_mode);
-        if (h_mode == kScrollbarAlwaysOn)
-          needs_horizontal_scrollbar = true;
-        else if (h_mode == kScrollbarAlwaysOff)
-          needs_horizontal_scrollbar = false;
-        if (v_mode == kScrollbarAlwaysOn)
-          needs_vertical_scrollbar = true;
-        else if (v_mode == kScrollbarAlwaysOff)
-          needs_vertical_scrollbar = false;
-      }
-    }
+    ScrollbarMode h_mode;
+    ScrollbarMode v_mode;
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
+    if (h_mode == kScrollbarAlwaysOn)
+      needs_horizontal_scrollbar = true;
+    else if (h_mode == kScrollbarAlwaysOff)
+      needs_horizontal_scrollbar = false;
+    if (v_mode == kScrollbarAlwaysOn)
+      needs_vertical_scrollbar = true;
+    else if (v_mode == kScrollbarAlwaysOff)
+      needs_vertical_scrollbar = false;
   }
 }
 
@@ -1780,7 +1771,7 @@ void PaintLayerScrollableArea::UpdateScrollableAreaSet(bool has_overflow) {
   if (Box().IsLayoutView()) {
     ScrollbarMode h_mode;
     ScrollbarMode v_mode;
-    frame_view->CalculateScrollbarModes(h_mode, v_mode);
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
     if (h_mode == kScrollbarAlwaysOff && v_mode == kScrollbarAlwaysOff)
       has_overflow = false;
   }