Make |HonorEditingBoundaryAtOrAfter()| to work correctly for nested editable

This patch changes |HonorEditingBoundaryAtOrAfter()| to handle nested editable.

Before this patch, |HonorEditingBoundaryAtOrAfter()| returns null position for
editable position anchored by non-editable position.

After this patch, |HonorEditingBoundaryAtOrAfter()| returns the last position in
the highest non-editable ancestor of |anchor|

Note: This patch is a preparation of the patch[1] which changes finding word
boundary in the block instead of inside editing boundary.

Example:
In below HTML, current code finds word boundary in "ABC", but the patch[1]
finds from "abcABCdef".

<div contenteditable>abc<span contenteditable=false>A^BC</span>def</div>
where "^" is starting position to find word boundary.

[1] http://crrev.com/c/737981 Simplify word granularity handling

Change-Id: I1fa702cba0bd48e8eec642c008ddda8fd063a6b8
Reviewed-on: https://chromium-review.googlesource.com/970130
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545031}

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

@@ -255,11 +255,18 @@ HonorEditingBoundaryAtOrAfterTemplate(
   if (HighestEditableRoot(pos.GetPosition()) == highest_root)
     return pos;
 
-  // Return empty position if this position is non-editable, but |pos| is
-  // editable.
-  // TODO(yosin) Move to the next non-editable region.
-  if (!highest_root)
+  // Returns the last position in the highest non-editable ancestor of |anchor|.
+  if (!highest_root) {
+    const Node* last_non_editable = anchor.ComputeContainerNode();
+    for (const Node& ancestor : Strategy::AncestorsOf(*last_non_editable)) {
+      if (HasEditableStyle(ancestor)) {
+        return PositionWithAffinityTemplate<Strategy>(
+            PositionTemplate<Strategy>::LastPositionInNode(*last_non_editable));
+      }
+      last_non_editable = &ancestor;
+    }
     return PositionWithAffinityTemplate<Strategy>();
+  }
 
   // Return the next position after |pos| that is in the same editable region
   // as this position

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

@@ -304,8 +304,8 @@ Position PreviousBoundary(const VisiblePosition&, BoundarySearchFunction);
 PositionInFlatTree PreviousBoundary(const VisiblePositionInFlatTree&,
                                     BoundarySearchFunction);
 
-PositionWithAffinity HonorEditingBoundaryAtOrAfter(const PositionWithAffinity&,
-                                                   const Position&);
+CORE_EXPORT PositionWithAffinity
+HonorEditingBoundaryAtOrAfter(const PositionWithAffinity&, const Position&);
 
 PositionInFlatTreeWithAffinity HonorEditingBoundaryAtOrAfter(
     const PositionInFlatTreeWithAffinity&,

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

@@ -7,6 +7,7 @@
 #include "bindings/core/v8/V8BindingForTesting.h"
 #include "core/dom/Text.h"
 #include "core/editing/PositionWithAffinity.h"
+#include "core/editing/SelectionTemplate.h"
 #include "core/editing/VisiblePosition.h"
 #include "core/editing/testing/EditingTestBase.h"
 #include "core/html/forms/TextControlElement.h"
@@ -222,6 +223,26 @@ TEST_F(VisibleUnitsTest, endOfDocument) {
           .DeepEquivalent());
 }
 
+TEST_F(VisibleUnitsTest, HonorEditingBoundaryAtOrAfterNestedEditable) {
+  const SelectionInDOMTree& selection = SetSelectionTextToBody(
+      "<div contenteditable>"
+      "abc"
+      "<span contenteditable=\"false\">A^BC</span>"
+      "d|ef"
+      "</div>");
+  const PositionWithAffinity& result = HonorEditingBoundaryAtOrAfter(
+      PositionWithAffinity(selection.Extent()), selection.Base());
+  ASSERT_TRUE(result.IsNotNull());
+  EXPECT_EQ(
+      "<div contenteditable>"
+      "abc"
+      "<span contenteditable=\"false\">ABC|</span>"
+      "def"
+      "</div>",
+      GetCaretTextFromBody(result.GetPosition()));
+  EXPECT_EQ(TextAffinity::kDownstream, result.Affinity());
+}
+
 TEST_F(VisibleUnitsTest, isEndOfEditableOrNonEditableContent) {
   const char* body_content =
       "<a id=host><b id=one contenteditable>1</b><b id=two>22</b></a>";