[Android] Add slack to allow refresh after overscrolling

content/browser/android/overscroll_glow.cc

 // Copyright (c) 2013 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/overscroll_glow.h"
 
 #include "cc/layers/layer.h"
 #include "content/browser/android/edge_effect_base.h"
 
 using std::max;
@@ skipping 84 matching lines @@
 bool OverscrollGlow::IsActive() const {
   if (!initialized_)
     return false;
   for (size_t i = 0; i < EDGE_COUNT; ++i) {
     if (!edge_effects_[i]->IsFinished())
       return true;
   }
   return false;
 }
 
+float OverscrollGlow::GetVisibleAlpha() const {
+  float max_alpha = 0;
+  for (size_t i = 0; i < EDGE_COUNT; ++i) {
+    if (!edge_effects_[i]->IsFinished())
+      max_alpha = std::max(max_alpha, edge_effects_[i]->GetAlpha());
+  }
+  return std::min(max_alpha, 1.f);
+}
+
 bool OverscrollGlow::OnOverscrolled(base::TimeTicks current_time,
                                     gfx::Vector2dF accumulated_overscroll,
                                     gfx::Vector2dF overscroll_delta,
                                     gfx::Vector2dF velocity,
                                     gfx::Vector2dF displacement) {
   // The size of the glow determines the relative effect of the inputs; an
   // empty-sized effect is effectively disabled.
   if (viewport_size_.IsEmpty())
     return false;
 
@@ skipping 173 matching lines @@
   for (size_t i = 0; i < EDGE_COUNT; ++i)
     edge_effects_[i]->Release(current_time);
 }
 
 EdgeEffectBase* OverscrollGlow::GetOppositeEdge(int edge_index) {
   DCHECK(initialized_);
   return edge_effects_[(edge_index + 2) % EDGE_COUNT].get();
 }
 
 }  // namespace content