Tracking text selection on the browser side in OOPIF.

content/browser/renderer_host/render_widget_host_view_base.h

Index: content/browser/renderer_host/render_widget_host_view_base.h
diff --git a/content/browser/renderer_host/render_widget_host_view_base.h b/content/browser/renderer_host/render_widget_host_view_base.h
index 756a7d834aa7155016516108d276c606b6723b6e..4b39b9ac3ef55c98b83db43f6eca5f703c21805b 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.h
+++ b/content/browser/renderer_host/render_widget_host_view_base.h
@@ -432,6 +432,11 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
   // Whether we are showing a context menu.
   bool showing_context_menu_;
 
+// TODO(ekaramad): In aura, text selection tracking for IME is done through the
+// TextInputManager. We still need the following variables for other platforms.
+// Remove them when tracking is done by TextInputManager on all platforms
+// (https://crbug.com/578168).
+#if !defined(USE_AURA)
   // A buffer containing the text inside and around the current selection range.
   base::string16 selection_text_;
 
@@ -441,6 +446,7 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
 
   // The current selection range relative to the start of the web page.
   gfx::Range selection_range_;
+#endif
 
   // The scale factor of the display the renderer is currently on.
   float current_device_scale_factor_;
@@ -461,6 +467,9 @@ class CONTENT_EXPORT RenderWidgetHostViewBase : public RenderWidgetHostView,
  private:
   void FlushInput();
 
+  // The non-const implementation of RenderWidgetHostView::GetSelectedText().

[kenrb, 2016/07/12 19:15:25]

Why is this needed? There is only one caller, which can access the selected text
directly.

[EhsanK, 2016/07/12 19:33:48]

The idea was to remove |selection_text_|, |selection_text_offset_|, and
|selection_range_| from this into TextInputManager. The only reason I have not
remove them yet is that Mac uses them so I will have to wait until I start
working on Mac code. Then these will be removed. So for this CL, I pretend they
do not exist and the state is only tracked at TextInputManager.

Now to implement RenderWidgetHostView::GetSelectedText(), I cannot simply call
GetTextInputManager() since GetSelectedText() is const but GetTextInputManager()
and TextInputManager::GetTextSelection are not. So I implemented this extra
method which is not const, and then I call it, after const_cast, from
GetSelectedText().

I am not particularly happy with this const_cast myself, but I could not come up
with a less messy way of getting around this problem.

[kenrb, 2016/07/12 20:15:17]

Yeah, this isn't good. Basically it is trying to cheat on this method being
const.

It looks like TextInputManager::GetTextSelection() should be const to begin
with, which is part of the problem. GetTextInputManager() could almost be const,
but it can lazily create the TextInputManager. Can you make
GetTextInputManager() const if you make text_input_manager_ mutable? That seems
like the right way to do this.

[EhsanK, 2016/07/18 15:21:29]

So basically we ended up removing const from this method altogether (in a
separate CL). So the new version does not have the same issue.

+  base::string16 GetSelectedTextFromTextInputManager();
+
   gfx::Rect current_display_area_;
 
   uint32_t renderer_frame_number_;