Check frame for nullptr in AutoscrollController::animate

third_party/WebKit/Source/core/page/AutoscrollController.cpp

Index: third_party/WebKit/Source/core/page/AutoscrollController.cpp
diff --git a/third_party/WebKit/Source/core/page/AutoscrollController.cpp b/third_party/WebKit/Source/core/page/AutoscrollController.cpp
index 34620a291a0f193b9ce7d0e5e8744a84ed516de0..2721ae0b8c0981cb89d71bba4cb9e82763a93c65 100644
--- a/third_party/WebKit/Source/core/page/AutoscrollController.cpp
+++ b/third_party/WebKit/Source/core/page/AutoscrollController.cpp
@@ -241,19 +241,21 @@ void AutoscrollController::animate(double)
         return;
     }
 
-    EventHandler& eventHandler = m_autoscrollLayoutObject->frame()->eventHandler();

[dtapuska, 2016/09/08 14:13:20]

I was kind of anticipating a change like

LocalFrame* frame = m_autoscrollLayoutObject->frame();
if (!frame) {
  stopAutoscroll();
  return;
}
...

I think this can still cause a crash on line: 
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/page/Auto...

whereas the way I was thinking it wouldn't. Sorry for my delay on the review.

     switch (m_autoscrollType) {
     case AutoscrollForDragAndDrop:
         if (WTF::currentTime() - m_dragAndDropAutoscrollStartTime > autoscrollDelay)
             m_autoscrollLayoutObject->autoscroll(m_dragAndDropAutoscrollReferencePosition);
         break;
     case AutoscrollForSelection:
-        if (!eventHandler.mousePressed()) {
-            stopAutoscroll();
-            return;
+        if (LocalFrame* frame = m_autoscrollLayoutObject->frame()) {
+            EventHandler& eventHandler = frame->eventHandler();
+            if (!eventHandler.mousePressed()) {
+                stopAutoscroll();
+                return;
+            }
+            eventHandler.updateSelectionForMouseDrag();
+            m_autoscrollLayoutObject->autoscroll(eventHandler.lastKnownMousePosition());
         }
-        eventHandler.updateSelectionForMouseDrag();
-        m_autoscrollLayoutObject->autoscroll(eventHandler.lastKnownMousePosition());
         break;
     case NoAutoscroll:
         break;
@@ -264,8 +266,12 @@ void AutoscrollController::animate(double)
             stopAutoscroll();
             return;
         }
-        if (FrameView* view = m_autoscrollLayoutObject->frame()->view())
-            updatePanScrollState(view, eventHandler.lastKnownMousePosition());
+        if (LocalFrame* frame = m_autoscrollLayoutObject->frame()) {
+            if (FrameView* view = frame->view()) {
+                EventHandler& eventHandler = frame->eventHandler();
+                updatePanScrollState(view, eventHandler.lastKnownMousePosition());
+            }
+        }
         m_autoscrollLayoutObject->panScroll(m_panScrollStartPos);
         break;
 #endif