Update touch selection to only modify one selection point at a time.

content/browser/renderer_host/input/input_router_impl.cc

Index: content/browser/renderer_host/input/input_router_impl.cc
diff --git a/content/browser/renderer_host/input/input_router_impl.cc b/content/browser/renderer_host/input/input_router_impl.cc
index 441f9384bb8745e05efd53d9e1e645aa94255124..d940e239f6834f8da63ac2ef5650540fff412a71 100644
--- a/content/browser/renderer_host/input/input_router_impl.cc
+++ b/content/browser/renderer_host/input/input_router_impl.cc
@@ -69,6 +69,7 @@ InputRouterImpl::InputRouterImpl(IPC::Sender* sender,
       ack_handler_(ack_handler),
       routing_id_(routing_id),
       select_range_pending_(false),
+      move_selection_extent_pending_(false),
       move_caret_pending_(false),
       mouse_move_pending_(false),
       mouse_wheel_pending_(false),
@@ -96,6 +97,8 @@ bool InputRouterImpl::SendInput(scoped_ptr<IPC::Message> message) {
     // Check for types that require an ACK.
     case InputMsg_SelectRange::ID:
       return SendSelectRange(message.Pass());
+    case InputMsg_MoveSelectionExtent::ID:
+      return SendMoveSelectionExtent(message.Pass());
     case InputMsg_MoveCaret::ID:
       return SendMoveCaret(message.Pass());
     case InputMsg_HandleInputEvent::ID:
@@ -269,6 +272,8 @@ bool InputRouterImpl::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(InputHostMsg_DidOverscroll, OnDidOverscroll)
     IPC_MESSAGE_HANDLER(ViewHostMsg_MoveCaret_ACK, OnMsgMoveCaretAck)
     IPC_MESSAGE_HANDLER(ViewHostMsg_SelectRange_ACK, OnSelectRangeAck)
+    IPC_MESSAGE_HANDLER(ViewHostMsg_MoveSelectionExtent_ACK,
+                        OnMoveSelectionExtentAck)
     IPC_MESSAGE_HANDLER(ViewHostMsg_HasTouchEventHandlers,
                         OnHasTouchEventHandlers)
     IPC_MESSAGE_HANDLER(InputHostMsg_SetTouchAction,
@@ -309,6 +314,18 @@ bool InputRouterImpl::SendSelectRange(scoped_ptr<IPC::Message> message) {
   return Send(message.release());
 }
 
+bool InputRouterImpl::SendMoveSelectionExtent(
+    scoped_ptr<IPC::Message> message) {
+  DCHECK(message->type() == InputMsg_SelectRange::ID);
+  if (move_selection_extent_pending_) {

[jdduke (slow), 2014/10/15 15:46:07]

There's probably some common logic between SelectRange/MoveCaret/MoveExtent we
could factor out, but that's probably best left as a follow-up patch. Maybe add
a:

// TODO(jdduke): Factor out common logic between selection and caret-related IPC
messages.

[christiank, 2014/10/17 14:33:05]

Yes, I noticed this. I didn't address it in this CL since I wanted to keep it
small and focused :) A TODO makes perfect sense!

+    next_selection_extent_move_ = message.Pass();
+    return true;
+  }
+
+  move_selection_extent_pending_ = true;
+  return Send(message.release());
+}
+
 bool InputRouterImpl::SendMoveCaret(scoped_ptr<IPC::Message> message) {
   DCHECK(message->type() == InputMsg_MoveCaret::ID);
   if (move_caret_pending_) {
@@ -493,6 +510,12 @@ void InputRouterImpl::OnSelectRangeAck() {
     SendSelectRange(next_selection_range_.Pass());
 }
 
+void InputRouterImpl::OnMoveSelectionExtentAck() {
+  move_selection_extent_pending_ = false;
+  if (next_selection_extent_move_)
+    SendMoveSelectionExtent(next_selection_extent_move_.Pass());
+}
+
 void InputRouterImpl::OnHasTouchEventHandlers(bool has_handlers) {
   TRACE_EVENT1("input", "InputRouterImpl::OnHasTouchEventHandlers",
                "has_handlers", has_handlers);
@@ -680,6 +703,7 @@ bool InputRouterImpl::HasPendingEvents() const {
          mouse_move_pending_ ||
          mouse_wheel_pending_ ||
          select_range_pending_ ||
+         move_selection_extent_pending_ ||
          move_caret_pending_;
 }