Ensure the scheduler always changes from UseCase LOADING to NONE.

third_party/WebKit/Source/core/paint/FirstMeaningfulPaintDetectorTest.cpp

 // 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 "core/paint/FirstMeaningfulPaintDetector.h"
 
 #include "core/paint/PaintTiming.h"
 #include "core/testing/DummyPageHolder.h"
 #include "platform/scheduler/test/fake_web_task_runner.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 140 matching lines @@
   simulateLayoutAndPaint(10);
   // The second candidate gets reported.
   EXPECT_GT(paintTiming().firstMeaningfulPaintCandidate(), afterPaint);
   double candidate = paintTiming().firstMeaningfulPaintCandidate();
   // The third candidate gets ignored since we already saw the first candidate.
   simulateLayoutAndPaint(10);
   EXPECT_EQ(paintTiming().firstMeaningfulPaintCandidate(), candidate);
 }
 
 TEST_F(FirstMeaningfulPaintDetectorTest,
+       OnlyOneFirstMeaningfulPaintCandidateBeforeNetworkStable) {
+  paintTiming().markFirstContentfulPaint();
+  EXPECT_EQ(paintTiming().firstMeaningfulPaintCandidate(), 0.0);
+  double beforePaint = monotonicallyIncreasingTime();
+  simulateLayoutAndPaint(1);
+  // The first candidate is initially ignored.
+  EXPECT_EQ(paintTiming().firstMeaningfulPaintCandidate(), 0.0);
+  simulateNetworkStable();
+  // The networkStable then promotes the first candidate.
+  EXPECT_GT(paintTiming().firstMeaningfulPaintCandidate(), beforePaint);
+  double candidate = paintTiming().firstMeaningfulPaintCandidate();
+  // The second candidate is then ignored.
+  simulateLayoutAndPaint(10);
+  EXPECT_EQ(paintTiming().firstMeaningfulPaintCandidate(), candidate);
+}
+
+TEST_F(FirstMeaningfulPaintDetectorTest,
        NetworkStableBeforeFirstContentfulPaint) {
   paintTiming().markFirstPaint();
   simulateLayoutAndPaint(1);
   simulateNetworkStable();
   EXPECT_EQ(paintTiming().firstMeaningfulPaint(), 0.0);
   paintTiming().markFirstContentfulPaint();
   simulateNetworkStable();
   EXPECT_NE(paintTiming().firstMeaningfulPaint(), 0.0);
 }
 
@@ skipping 61 matching lines @@
   EXPECT_FALSE(isNetwork2QuietTimerRestarted());
 
   setActiveConnections(0);
   EXPECT_TRUE(isNetwork0QuietTimerActive());
   EXPECT_TRUE(isNetwork0QuietTimerRestarted());
   EXPECT_TRUE(isNetwork2QuietTimerActive());
   EXPECT_FALSE(isNetwork2QuietTimerRestarted());
 }
 
 }  // namespace blink