Reland: Implement Aura side of unified touch text selection for contents

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index c512d41fce1f9ef2586cbe2d416d3b84e793210e..ea8f9197571f47b64fc02d3e71668265b3f59d45 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -2013,10 +2013,20 @@ void RenderWidget::UpdateSelectionBounds() {
   if (handling_ime_event_)
     return;
 
+#if defined(USE_AURA)
+  // TODO(mohsen): For now, always send explicit selection IPC notifications for
+  // Aura beucause composited selection updates are not working for webview tags
+  // which regresses IME inside webview. Remove this when composited selection
+  // updates are fixed for webviews.
+  bool send_ipc = true;

[jdduke (slow), 2015/07/08 15:22:42]

This is pretty scary. Do we know why this isn't working? How does the IME use
this data? Should we only send it when for webview instances (do we have that
info available here?)?

[mohsen, 2015/07/08 21:26:18]

IME uses cursor location to show a popup when user changes the keyboard layout
language. For webview, it is not working with composited selection updates
because selection bounds are not propagated to the embedder RenderWidgetHostView
properly. We are working on a fix for that and also touch selection in general,
for webview (see http://crrev.com/1203223002 for some discussions).

I think sending this IPC only for webview would complicate the code as there
would be two different paths to update selection bounds for IME. Currently, my
patch sends both updates, but touch selection only uses one and IME only uses
the other.

+#else
   // With composited selection updates, the selection bounds will be reported
   // directly by the compositor, in which case explicit IPC selection
   // notifications should be suppressed.
-  if (!blink::WebRuntimeFeatures::isCompositedSelectionUpdateEnabled()) {
+  bool send_ipc =
+      !blink::WebRuntimeFeatures::isCompositedSelectionUpdateEnabled();
+#endif
+  if (send_ipc) {
     ViewHostMsg_SelectionBounds_Params params;
     GetSelectionBounds(&params.anchor_rect, &params.focus_rect);
     if (selection_anchor_rect_ != params.anchor_rect ||