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

content/browser/android/content_view_core_impl.cc

 // Copyright 2012 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/android/content_view_core_impl.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
@@ skipping 759 matching lines @@
   root_layer_->SetIsDrawable(false);
 }
 
 void ContentViewCoreImpl::RemoveLayer(scoped_refptr<cc::Layer> layer) {
   layer->RemoveFromParent();
 
   if (!root_layer_->children().size())
     root_layer_->SetIsDrawable(true);
 }
 
-void ContentViewCoreImpl::SelectBetweenCoordinates(const gfx::PointF& start,
-                                                   const gfx::PointF& end) {
+void ContentViewCoreImpl::MoveRangeSelectionExtent(
+    const gfx::PointF& position) {

[jdduke (slow), 2014/10/21 16:57:36]

Nit: Let's call this |extent| instead of |position| (sorry for the code
thrashing!).

   if (!web_contents_)
     return;
 
-  gfx::Point start_point = gfx::Point(start.x(), start.y());
-  gfx::Point end_point = gfx::Point(end.x(), end.y());
-  if (start_point == end_point)
+  web_contents_->MoveRangeSelectionExtent(
+      gfx::Point(position.x(), position.y()));
+}
+
+void ContentViewCoreImpl::SelectBetweenCoordinates(const gfx::PointF& base,
+                                                   const gfx::PointF& extent) {
+  if (!web_contents_)
     return;
 
-  web_contents_->SelectRange(start_point, end_point);
+  gfx::Point base_point = gfx::Point(base.x(), base.y());
+  gfx::Point extent_point = gfx::Point(extent.x(), extent.y());
+  if (base_point == extent_point)
+    return;
+
+  web_contents_->SelectRange(base_point, extent_point);
 }
 
 ui::ViewAndroid* ContentViewCoreImpl::GetViewAndroid() const {
   return view_android_;
 }
 
 ui::WindowAndroid* ContentViewCoreImpl::GetWindowAndroid() const {
   return window_android_;
 }
 
@@ skipping 537 matching lines @@
       reinterpret_cast<ui::WindowAndroid*>(window_android),
       retained_objects_set);
   return reinterpret_cast<intptr_t>(view);
 }
 
 bool RegisterContentViewCore(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace content