Consider editability when looking for a caret position

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

Index: third_party/WebKit/Source/core/editing/VisibleUnits.cpp
diff --git a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
index 8abdcb4c98eaff5baac6ead9d0b929fd4ad0cf91..ae37d3d18e9ba048f1e0c508897f2a077d313a3a 100644
--- a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
+++ b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
@@ -2241,7 +2241,9 @@ static bool isNonTextLeafChild(LayoutObject* object) {
   return true;
 }
 
-static InlineTextBox* searchAheadForBetterMatch(LayoutObject* layoutObject) {
+static InlineTextBox* searchAheadForBetterMatch(
+    LayoutObject* layoutObject,
+    EditingBoundaryCrossingRule rule) {
   LayoutBlock* container = layoutObject->containingBlock();
   for (LayoutObject* next = layoutObject->nextInPreOrder(container); next;
        next = next->nextInPreOrder(container)) {
@@ -2252,6 +2254,9 @@ static InlineTextBox* searchAheadForBetterMatch(LayoutObject* layoutObject) {
     if (isNonTextLeafChild(next))
       return 0;
     if (next->isText()) {
+      if (rule == CannotCrossEditingBoundary &&
+          next->style()->userModify() == READ_ONLY)
+        return 0;
       InlineTextBox* match = 0;
       int minOffset = INT_MAX;
       for (InlineTextBox* box = toLayoutText(next)->firstTextBox(); box;
@@ -2324,6 +2329,10 @@ static InlineBoxPosition computeInlineBoxPositionTemplate(
     if (canHaveChildrenForEditing(anchorNode) &&
         layoutObject->isLayoutBlockFlow() &&
         hasRenderedNonAnonymousDescendantsWithHeight(layoutObject)) {
+      if (layoutObject->isLayoutBlock() &&
+          toLayoutBlock(layoutObject)->childrenInline()) {
+        return InlineBoxPosition(inlineBox, caretOffset);
+      }
       // Try a visually equivalent position with possibly opposite
       // editability. This helps in case |this| is in an editable block
       // but surrounded by non-editable positions. It acts to negate the
@@ -2377,7 +2386,10 @@ static InlineBoxPosition computeInlineBoxPositionTemplate(
     }
     if (candidate && candidate == textLayoutObject->lastTextBox() &&
         affinity == TextAffinity::Downstream) {
-      box = searchAheadForBetterMatch(textLayoutObject);
+      box = searchAheadForBetterMatch(textLayoutObject,
+                                      hasEditableStyle(*anchorNode)
+                                          ? CannotCrossEditingBoundary
+                                          : CanCrossEditingBoundary);
       if (box)
         caretOffset = box->caretMinOffset();
     }