Adds the concept of Policies to the Blink Scheduler

Source/platform/scheduler/SchedulerTest.cpp

Index: Source/platform/scheduler/SchedulerTest.cpp
diff --git a/Source/platform/scheduler/SchedulerTest.cpp b/Source/platform/scheduler/SchedulerTest.cpp
index 40b8a7cc62a6bcea7114b4b316256d28975aca61..2ce6714f43c3b72bb6ec309b485d500ea2d8407e 100644
--- a/Source/platform/scheduler/SchedulerTest.cpp
+++ b/Source/platform/scheduler/SchedulerTest.cpp
@@ -76,6 +76,12 @@ public:
         , m_sharedTimerRunning(false)
         , m_sharedTimerFireInterval(0)
     {
+        WTF::setMonotonicallyIncreasingTimeFunction(getDebugTime);

[Sami, 2014/09/10 16:00:39]

Maybe getMonotonicTimeForTest?

[alexclarke, 2014/09/10 17:35:37]

Done.

+    }
+
+    virtual ~SchedulerTestingPlatformSupport()
+    {
+        WTF::setMonotonicallyIncreasingTimeFunction(0);

[Sami, 2014/09/10 16:00:39]

I hope we're not stomping over some other test by doing this :P

[alexclarke, 2014/09/10 17:35:37]

Likewise.  If it turns out we are, then we can just save and restore it. 
Although that means adding a (trivial) function in WTF to get the current
function.

     }
 
     // blink::Platform implementation.
@@ -89,6 +95,11 @@ public:
         m_sharedTimerFunction = timerFunction;
     }
 
+    virtual double monotonicallyIncreasingTime() OVERRIDE
+    {
+        return s_debugTime;
+    }
+
     virtual void setSharedTimerFireInterval(double)
     {
         m_sharedTimerFireInterval = 0;
@@ -125,13 +136,27 @@ public:
         return m_mainThread.numPendingMainThreadTasks();
     }
 
+    static void setDebugTime(double time)
+    {
+        s_debugTime = time;
+    }
+
 private:
+    static double getDebugTime(void)
+    {
+        return s_debugTime;
+    }
+
     TestMainThread m_mainThread;
     SharedTimerFunction m_sharedTimerFunction;
     bool m_sharedTimerRunning;
     double m_sharedTimerFireInterval;
+
+    static double s_debugTime;
 };
 
+double SchedulerTestingPlatformSupport::s_debugTime = 0;
+
 class SchedulerTest : public testing::Test {
 public:
     SchedulerTest()
@@ -399,4 +424,47 @@ TEST_F(SchedulerTest, HighPriorityTasksOnlyRunOncePerSharedTimerFiring)
     m_scheduler->setSharedTimerFiredFunction(nullptr);
 }
 
+TEST_F(SchedulerTest, TestInputEventTriggersShouldYield)
+{
+    ASSERT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+    m_scheduler->postInputTask(FROM_HERE, WTF::bind(&dummyTask));
+
+    EXPECT_TRUE(m_scheduler->shouldYieldForHighPriorityWork());
+}
+
+TEST_F(SchedulerTest, TestCompositorEventDoesNotTriggerShouldYield_InNormalMode)
+{
+    ASSERT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+    m_scheduler->postCompositorTask(FROM_HERE, WTF::bind(&dummyTask));
+
+    EXPECT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+}
+
+TEST_F(SchedulerTest, TestInputEventTriggersLowLatencyMode)
+{
+    // Fire off an input task to put us in low latency mode.
+    m_scheduler->postInputTask(FROM_HERE, WTF::bind(&dummyTask));
+    runPendingTasks();
+
+    ASSERT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+    m_scheduler->postCompositorTask(FROM_HERE, WTF::bind(&dummyTask));
+
+    EXPECT_TRUE(m_scheduler->shouldYieldForHighPriorityWork());
+}
+
+TEST_F(SchedulerTest, TestCompositorEvent_LowLatencyModeDoesntLastLongWithoutInputEvents)
+{
+    SchedulerTestingPlatformSupport::setDebugTime(1000.0);
+
+    // Fire off an input task to put us in low latency mode.
+    m_scheduler->postInputTask(FROM_HERE, WTF::bind(&dummyTask));
+    SchedulerTestingPlatformSupport::setDebugTime(1000.5);
+    runPendingTasks();
+
+    ASSERT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+    m_scheduler->postCompositorTask(FROM_HERE, WTF::bind(&dummyTask));
+
+    EXPECT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
+}
+
 } // namespace