[Android] Fix Text selection with Stylus button pressed from Android M

content/browser/renderer_host/input/stylus_text_selector.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/input/stylus_text_selector.h"
 
 #include "ui/events/event_constants.h"
 #include "ui/events/gesture_detection/gesture_detector.h"
 #include "ui/events/gesture_detection/gesture_provider_config_helper.h"
 #include "ui/events/gesture_detection/motion_event.h"
@@ skipping 39 matching lines @@
 
 bool StylusTextSelector::OnTouchEvent(const MotionEvent& event) {
   // Only trigger selection on ACTION_DOWN to prevent partial touch or gesture
   // sequences from being forwarded.
   if (event.GetAction() == MotionEvent::ACTION_DOWN)
     text_selection_triggered_ = ShouldStartTextSelection(event);
 
   if (!text_selection_triggered_)
     return false;
 
+  // For Android version < M, stylus button pressed state is BUTTON_SECONDARY.
+  // From Android M, this state has changed to BUTTON_STYLUS_PRIMARY.
   secondary_button_pressed_ =
-      event.GetButtonState() == MotionEvent::BUTTON_SECONDARY;
+      event.GetButtonState() == MotionEvent::BUTTON_SECONDARY ||
+      event.GetButtonState() == MotionEvent::BUTTON_STYLUS_PRIMARY;
 
   switch (event.GetAction()) {
     case MotionEvent::ACTION_DOWN:
       drag_state_ = NO_DRAG;
       anchor_x_ = event.GetX();
       anchor_y_ = event.GetY();
       break;
 
     case MotionEvent::ACTION_MOVE:
       if (!secondary_button_pressed_) {
@@ skipping 61 matching lines @@
   }
 
   return true;
 }
 
 // static
 bool StylusTextSelector::ShouldStartTextSelection(const MotionEvent& event) {
   DCHECK_GT(event.GetPointerCount(), 0u);
   // Currently we are supporting stylus-only cases.
   const bool is_stylus = event.GetToolType(0) == MotionEvent::TOOL_TYPE_STYLUS;
+
+  // For Android version < M, stylus button pressed state is BUTTON_SECONDARY.
+  // From Android M, this state has changed to BUTTON_STYLUS_PRIMARY.
   const bool is_only_secondary_button_pressed =
-      event.GetButtonState() == MotionEvent::BUTTON_SECONDARY;
+      event.GetButtonState() == MotionEvent::BUTTON_SECONDARY ||
+      event.GetButtonState() == MotionEvent::BUTTON_STYLUS_PRIMARY;
   return is_stylus && is_only_secondary_button_pressed;
 }
 
 }  // namespace content