Protect AudioScheduledSoureNode::m_startTime and m_endTime.

Source/modules/webaudio/AudioScheduledSourceNode.cpp

Index: Source/modules/webaudio/AudioScheduledSourceNode.cpp
diff --git a/Source/modules/webaudio/AudioScheduledSourceNode.cpp b/Source/modules/webaudio/AudioScheduledSourceNode.cpp
index d853761f1b983b2da6e9abf08075d2c58e9f99da..7c3db4dd361cfdcf38500906d5ed6d6338e4e7ea 100644
--- a/Source/modules/webaudio/AudioScheduledSourceNode.cpp
+++ b/Source/modules/webaudio/AudioScheduledSourceNode.cpp
@@ -41,9 +41,9 @@ const double AudioScheduledSourceHandler::UnknownTime = -1;
 
 AudioScheduledSourceHandler::AudioScheduledSourceHandler(NodeType nodeType, AudioNode& node, float sampleRate)
     : AudioHandler(nodeType, node, sampleRate)
+    , m_hasEndedListener(false)
     , m_startTime(0)
     , m_endTime(UnknownTime)
-    , m_hasEndedListener(false)
     , m_playbackState(UNSCHEDULED_STATE)
 {
 }
@@ -67,11 +67,12 @@ void AudioScheduledSourceHandler::updateSchedulingInfo(
     // endFrame              : End frame for this source.
     size_t quantumStartFrame = context()->currentSampleFrame();
     size_t quantumEndFrame = quantumStartFrame + quantumFrameSize;
-    size_t startFrame = AudioUtilities::timeToSampleFrame(m_startTime, sampleRate);
-    size_t endFrame = m_endTime == UnknownTime ? 0 : AudioUtilities::timeToSampleFrame(m_endTime, sampleRate);
+    size_t startFrame = AudioUtilities::timeToSampleFrame(startTime(), sampleRate);
+    double currentEndTime = endTime();
+    size_t endFrame = currentEndTime == UnknownTime ? 0 : AudioUtilities::timeToSampleFrame(currentEndTime, sampleRate);
 
     // If we know the end time and it's already passed, then don't bother doing any more rendering this cycle.
-    if (m_endTime != UnknownTime && endFrame <= quantumStartFrame)
+    if (currentEndTime != UnknownTime && endFrame <= quantumStartFrame)
         finish();
 
     PlaybackState state = playbackState();
@@ -109,7 +110,7 @@ void AudioScheduledSourceHandler::updateSchedulingInfo(
     // Handle silence after we're done playing.
     // If the end time is somewhere in the middle of this time quantum, then zero out the
     // frames from the end time to the very end of the quantum.
-    if (m_endTime != UnknownTime && endFrame >= quantumStartFrame && endFrame < quantumEndFrame) {
+    if (currentEndTime != UnknownTime && endFrame >= quantumStartFrame && endFrame < quantumEndFrame) {
         size_t zeroStartFrame = endFrame - quantumStartFrame;
         size_t framesToZero = quantumFrameSize - zeroStartFrame;
 
@@ -160,7 +161,7 @@ void AudioScheduledSourceHandler::start(double when, ExceptionState& exceptionSt
 
     // If |when| < currentTime, the source must start now according to the spec.
     // So just set startTime to currentTime in this case to start the source now.
-    m_startTime = std::max(when, context()->currentTime());
+    setStartTime(std::max(when, context()->currentTime()));
 
     setPlaybackState(SCHEDULED_STATE);
 }
@@ -190,7 +191,7 @@ void AudioScheduledSourceHandler::stop(double when, ExceptionState& exceptionSta
     // source has already stopped due to earlier calls to stop. No exceptions are thrown in any
     // case.
     when = std::max(0.0, when);
-    m_endTime = when;
+    setEndTime(when);
 }
 
 void AudioScheduledSourceHandler::finishWithoutOnEnded()