Fix issues related to rect elements

This CL fixes two issues:
1. transitioned based on edge_color_ for foreground animation. Previously, we
transition based on center_color_.
2. use alpha channel in the SkColor correctly. Previously, the alpha channel
in SkColor didn't apply to its RGB channel before blending.

Bug: NONE
Change-Id: I3533c062d632412cd181d0ed89c770910e6d56e3
Reviewed-on: https://chromium-review.googlesource.com/747444
Commit-Queue: Biao She <bshe@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513122}

chrome/browser/vr/BUILD.gn

@@ -192,6 +192,7 @@ test("vr_common_unittests") {
     "databinding/vector_binding_unittest.cc",
     "elements/exit_prompt_unittest.cc",
     "elements/linear_layout_unittest.cc",
+    "elements/rect_unittest.cc",
     "elements/spinner_unittest.cc",
     "elements/throbber_unittest.cc",
     "elements/transient_element_unittest.cc",

chrome/browser/vr/elements/rect.cc

@@ -25,7 +25,7 @@ void Rect::SetCenterColor(SkColor color) {
 
 void Rect::SetEdgeColor(SkColor color) {
   animation_player().TransitionColorTo(last_frame_time(), FOREGROUND_COLOR,
-                                       center_color_, color);
+                                       edge_color_, color);
 }
 
 void Rect::NotifyClientColorAnimated(SkColor color,

chrome/browser/vr/elements/rect_unittest.cc

+// Copyright 2017 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/vr/elements/rect.h"
+
+#include "base/memory/ptr_util.h"
+#include "chrome/browser/vr/target_property.h"
+#include "chrome/browser/vr/test/animation_utils.h"
+#include "chrome/browser/vr/test/constants.h"
+#include "chrome/browser/vr/ui_scene.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace vr {
+
+TEST(Rect, SetColorCorrectly) {
+  auto rect = base::MakeUnique<Rect>();
+
+  EXPECT_NE(SK_ColorCYAN, rect->edge_color());
+  EXPECT_NE(SK_ColorCYAN, rect->center_color());
+
+  rect->SetColor(SK_ColorCYAN);
+  EXPECT_EQ(SK_ColorCYAN, rect->edge_color());
+  EXPECT_EQ(SK_ColorCYAN, rect->center_color());
+
+  rect->SetEdgeColor(SK_ColorRED);
+  rect->SetCenterColor(SK_ColorBLUE);
+
+  EXPECT_EQ(SK_ColorRED, rect->edge_color());
+  EXPECT_EQ(SK_ColorBLUE, rect->center_color());
+}
+
+TEST(Rect, AnimateColorCorrectly) {
+  UiScene scene;
+  auto element = base::MakeUnique<Rect>();
+  Rect* rect = element.get();
+  scene.AddUiElement(kRoot, std::move(element));
+
+  rect->SetEdgeColor(SK_ColorRED);
+  rect->SetCenterColor(SK_ColorBLUE);
+
+  rect->SetTransitionedProperties({BACKGROUND_COLOR, FOREGROUND_COLOR});
+  rect->SetColor(SK_ColorBLACK);
+
+  scene.OnBeginFrame(MsToTicks(1), kForwardVector);
+  EXPECT_EQ(SK_ColorRED, rect->edge_color());
+  EXPECT_EQ(SK_ColorBLUE, rect->center_color());
+
+  scene.OnBeginFrame(MsToTicks(5000), kForwardVector);
+  EXPECT_EQ(SK_ColorBLACK, rect->edge_color());
+  EXPECT_EQ(SK_ColorBLACK, rect->center_color());
+}
+
+}  // namespace vr

chrome/browser/vr/vr_shell_renderer.cc

@@ -318,7 +318,10 @@ static constexpr char const* kGradientQuadFragmentShader = SHADER(
     float mask = 1.0 - step(1.0, length(v_CornerPosition));
     // Add some noise to prevent banding artifacts in the gradient.
     float n = (fract(dot(v_Position.xy, vec2(12345.67, 456.7))) - 0.5) / 255.0;
-    gl_FragColor = (color + n) * u_Opacity * mask;
+
+    color = color + n;
+    color = vec4(color.rgb * color.a, color.a);
+    gl_FragColor = color * u_Opacity * mask;
   }
 );