Handle kInfiniteDuration start times in WatchTimeReporter.

These should not start the reporter but are possible. Due to the
statefulness of WTR this means we need a new "has valid start time"
flag which controls when reporting is running.

BUG=965820,967103
TEST=new unittest
R=sandersd

Change-Id: Ieeb125472609f2a0c3b027c9c43ab4ded7cb669a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1632893
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663930}

media/blink/watch_time_reporter.cc

@@ -350,14 +350,20 @@ bool WatchTimeReporter::ShouldReportingTimerRun() const {
   // TODO(dalecurtis): We should only consider |volume_| when there is actually
   // an audio track; requires updating lots of tests to fix.
   return ShouldReportWatchTime() && is_playing_ && volume_ && is_visible_ &&
-         !in_shutdown_ && !is_seeking_;
+         !in_shutdown_ && !is_seeking_ && has_valid_start_timestamp_;
 }
 
 void WatchTimeReporter::MaybeStartReportingTimer(
     base::TimeDelta start_timestamp) {
-  DCHECK_NE(start_timestamp, kInfiniteDuration);
   DCHECK_GE(start_timestamp, base::TimeDelta());
 
+  // It's possible for |current_time| to be kInfiniteDuration here if the page
+  // seeks to kInfiniteDuration (2**64 - 1) when Duration() is infinite. There
+  // is no possible elapsed watch time when this occurs, so don't start the
+  // WatchTimeReporter at this time. If a later seek puts us earlier in the
+  // stream this method will be called again after OnSeeking().
+  has_valid_start_timestamp_ = start_timestamp != kInfiniteDuration;
+
   // Don't start the timer if our state indicates we shouldn't; this check is
   // important since the various event handlers do not have to care about the
   // state of other events.

media/blink/watch_time_reporter.h

@@ -213,6 +213,7 @@ class MEDIA_BLINK_EXPORT WatchTimeReporter : base::PowerObserver {
   bool is_visible_ = true;
   bool is_seeking_ = false;
   bool in_shutdown_ = false;
+  bool has_valid_start_timestamp_ = false;
   double volume_ = 1.0;
 
   // Updated by UpdateSecondaryProperties(); controls timer state when

media/blink/watch_time_reporter_unittest.cc

@@ -659,6 +659,14 @@ TEST_P(WatchTimeReporterTest, WatchTimeReporter) {
   wtr_.reset();
 }
 
+TEST_P(WatchTimeReporterTest, WatchTimeReporterInfiniteStartTime) {
+  EXPECT_CALL(*this, GetCurrentMediaTime())
+      .WillRepeatedly(testing::Return(kInfiniteDuration));
+  Initialize(false, false, kSizeJustRight);
+  wtr_->OnPlaying();
+  EXPECT_FALSE(IsMonitoring());
+}
+
 TEST_P(WatchTimeReporterTest, WatchTimeReporterBasic) {
   constexpr base::TimeDelta kWatchTimeEarly = base::TimeDelta::FromSeconds(5);
   constexpr base::TimeDelta kWatchTimeLate = base::TimeDelta::FromSeconds(10);