VrShell: Allow native control of UI element opacity.

chrome/browser/android/vr_shell/ui_elements.cc

 // Copyright 2016 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 "chrome/browser/android/vr_shell/ui_elements.h"
 
 #include "base/logging.h"
 #include "chrome/browser/android/vr_shell/animation.h"
 #include "chrome/browser/android/vr_shell/easing.h"
 
@@ skipping 104 matching lines @@
           animation.from.push_back(rotation.x);
           animation.from.push_back(rotation.y);
           animation.from.push_back(rotation.z);
           animation.from.push_back(rotation.angle);
           break;
         case Animation::TRANSLATION:
           animation.from.push_back(translation.x);
           animation.from.push_back(translation.y);
           animation.from.push_back(translation.z);
           break;
+        case Animation::OPACITY:
+          animation.from.push_back(opacity);
+          break;
       }
     }
     CHECK_EQ(animation.from.size(), animation.to.size());
 
     std::vector<float> values(animation.from.size());
     for (std::size_t i = 0; i < animation.from.size(); ++i) {
       if (animation.to[i] == animation.from[i] ||
           time >= (animation.start + animation.duration)) {
         values[i] = animation.to[i];
         continue;
@@ skipping 28 matching lines @@
         rotation.y = values[1];
         rotation.z = values[2];
         rotation.angle = values[3];
         break;
       case Animation::TRANSLATION:
         CHECK_EQ(animation.from.size(), 3u);
         translation.x = values[0];
         translation.y = values[1];
         translation.z = values[2];
         break;
+      case Animation::OPACITY:
+        CHECK_EQ(animation.from.size(), 1u);
+        opacity = values[0];
+        break;
     }
   }
   for (auto it = animations.begin(); it != animations.end();) {
     const Animation& animation = **it;
     if (time >= (animation.start + animation.duration)) {
       it = animations.erase(it);
     } else {
       ++it;
     }
   }
 }
 
 }  // namespace vr_shell