Make DOMSelection cache Range

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

Index: third_party/WebKit/Source/core/editing/DOMSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/DOMSelection.cpp b/third_party/WebKit/Source/core/editing/DOMSelection.cpp
index 34c9a1c8e64719d26bfc41d5b133c9a5c5b780e6..ba1dd89a31a079f82a788ec5eca1be4636ba347b 100644
--- a/third_party/WebKit/Source/core/editing/DOMSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/DOMSelection.cpp
@@ -175,6 +175,8 @@ String DOMSelection::type() const {
 int DOMSelection::rangeCount() const {
   if (!isAvailable())
     return 0;
+  if (m_range)
+    return 1;
   return frame()->selection().isNone() ? 0 : 1;
 }
 
@@ -383,6 +385,7 @@ void DOMSelection::extend(Node* node,
   if (!isValidForPosition(node))
     return;
 
+  markRangeDirty();
   const Position& base = frame()->selection().base();
   if (base.isNull()) {
     // TODO(editing-dev): We should throw |InvalidStateError| if selection is
@@ -413,6 +416,15 @@ Range* DOMSelection::getRangeAt(int index, ExceptionState& exceptionState) {
   // If you're hitting this, you've added broken multi-range selection support
   DCHECK_EQ(rangeCount(), 1);
 
+  if (m_range)
+    return m_range;
+
+  Range* range = createRangeFromSelectionEditor();
+  cacheRangeIfAttachedToRootDocument(range);
+  return range;
+}
+
+Range* DOMSelection::createRangeFromSelectionEditor() {
   Position anchor = anchorPosition(visibleSelection());
   if (!anchor.anchorNode()->isInShadowTree())
     return frame()->selection().firstRange();
@@ -427,7 +439,19 @@ Range* DOMSelection::getRangeAt(int index, ExceptionState& exceptionState) {
                        focusOffset());
 }
 
+void DOMSelection::markRangeDirty() {
+  m_range = nullptr;
+}
+
+void DOMSelection::cacheRangeIfAttachedToRootDocument(Range* range) {
+  if (m_treeScope->parentTreeScope())
+    return;
+
+  m_range = range;
+}
+
 void DOMSelection::removeAllRanges() {
+  m_range = nullptr;
   if (!isAvailable())
     return;
   frame()->selection().clear();
@@ -463,6 +487,7 @@ void DOMSelection::addRange(Range* newRange) {
 
   if (selection.isNone()) {
     selection.setSelectedRange(EphemeralRange(newRange), VP_DEFAULT_AFFINITY);
+    cacheRangeIfAttachedToRootDocument(newRange);
     return;
   }
 
@@ -510,6 +535,7 @@ void DOMSelection::addRange(Range* newRange) {
       EphemeralRange(start->startPosition(), end->endPosition());
   TextAffinity affinity = selection.selection().affinity();
   selection.setSelectedRange(merged, affinity);
+  cacheRangeIfAttachedToRootDocument(createRange(merged));
 }
 
 void DOMSelection::deleteFromDocument() {
@@ -671,6 +697,7 @@ void DOMSelection::addConsoleError(const String& message) {
 
 DEFINE_TRACE(DOMSelection) {
   visitor->trace(m_treeScope);
+  visitor->trace(m_range);
   ContextClient::trace(visitor);
 }