[WebVTT] Update dom construction logic for timestamp per spec

According to the spec [1] we need to include optional components
and add leading zeros if required for timestamp construction.
[1]: https://w3c.github.io/webvtt/#dom-construction-rules

Bug: 786382
Change-Id: I2b7320bd6b187cb3b85a5532c0a0fd398b3888cf
Reviewed-on: https://chromium-review.googlesource.com/773763
Commit-Queue: srirama chandra sekhar <srirama.m@samsung.com>
Reviewed-by: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#517767}

third_party/WebKit/LayoutTests/external/wpt/webvtt/api/VTTCue/getCueAsHTML-expected.txt

@@ -9,7 +9,7 @@ PASS VTTCue.getCueAsHTML(), <ruby>
 PASS VTTCue.getCueAsHTML(), <rt>
 PASS VTTCue.getCueAsHTML(), <v>
 PASS VTTCue.getCueAsHTML(), <v a b>
-FAIL VTTCue.getCueAsHTML(), <1:00:00.500> assert_equals: data expected "01:00:00.500" but got "1:00:00.500"
+PASS VTTCue.getCueAsHTML(), <1:00:00.500>
 FAIL VTTCue.getCueAsHTML(), x\0 assert_equals: data expected "x\0" but got "x"
 Harness: the test ran to completion.
 

third_party/WebKit/LayoutTests/external/wpt/webvtt/parsing/cue-text-parsing/tests/timestamps-expected.txt

-This is a testharness.js-based test.
-PASS WebVTT cue data parser test timestamps - 54c245f3fbe7a3e25398b13971d44f2bb3a5f947
-PASS WebVTT cue data parser test timestamps - 5e190a1b4541fcb10e403af111c14ef152fecb0d
-PASS WebVTT cue data parser test timestamps - 92b97d3497836259e0b9305e27f2b91ea1dc9b31
-PASS WebVTT cue data parser test timestamps - 2f0e84518d356cb1e56a366296fa491c5bed1e3a
-FAIL WebVTT cue data parser test timestamps - 47fa4306a695161da88533d456ce94829e53b13d assert_equals: expected "#document-fragment\n| <?timestamp 00:00:00.500>" but got "#document-fragment\n| <?timestamp 00:00.500>"
-PASS WebVTT cue data parser test timestamps - c1036a4322c1852e02e5a1843a9a81dfca6d7af3
-PASS WebVTT cue data parser test timestamps - 70ec34d828ca661a583c651207becb968bb41653
-PASS WebVTT cue data parser test timestamps - 66ba641ff047a226fa60fe867fd2479d40f3ff0f
-PASS WebVTT cue data parser test timestamps - 398e8da1aaaf392739ca72057fef58bd5333f74d
-PASS WebVTT cue data parser test timestamps - 391fce67644cf4dd9967e1436d1449ef5baf675f
-Harness: the test ran to completion.
-

third_party/WebKit/LayoutTests/media/track/opera/track/webvtt/parsing-cue-data/tests/timestamps-expected.txt

-This is a testharness.js-based test.
-PASS WebVTT cue data parser test timestamps - 54c245f3fbe7a3e25398b13971d44f2bb3a5f947
-PASS WebVTT cue data parser test timestamps - 5e190a1b4541fcb10e403af111c14ef152fecb0d
-PASS WebVTT cue data parser test timestamps - 92b97d3497836259e0b9305e27f2b91ea1dc9b31
-FAIL WebVTT cue data parser test timestamps - 47fa4306a695161da88533d456ce94829e53b13d assert_equals: expected "#document-fragment\n| <?timestamp 00:00:00.500>" but got "#document-fragment\n| <?timestamp 00:00.500>"
-PASS WebVTT cue data parser test timestamps - c1036a4322c1852e02e5a1843a9a81dfca6d7af3
-PASS WebVTT cue data parser test timestamps - 70ec34d828ca661a583c651207becb968bb41653
-PASS WebVTT cue data parser test timestamps - 66ba641ff047a226fa60fe867fd2479d40f3ff0f
-PASS WebVTT cue data parser test timestamps - 398e8da1aaaf392739ca72057fef58bd5333f74d
-PASS WebVTT cue data parser test timestamps - 391fce67644cf4dd9967e1436d1449ef5baf675f
-Harness: the test ran to completion.
-

third_party/WebKit/Source/core/html/track/vtt/VTTParser.cpp

@@ -39,6 +39,7 @@
 #include "platform/loader/fetch/TextResourceDecoderOptions.h"
 #include "platform/runtime_enabled_features.h"
 #include "platform/text/SegmentedString.h"
+#include "platform/wtf/DateMath.h"
 #include "platform/wtf/text/CharacterNames.h"
 #include "platform/wtf/text/WTFString.h"
 
@@ -402,6 +403,18 @@ bool VTTParser::CollectTimeStamp(const String& line, double& time_stamp) {
   return CollectTimeStamp(input, time_stamp);
 }
 
+static String SerializeTimeStamp(double time_stamp) {
+  uint64_t value = clampTo<uint64_t>(time_stamp * 1000);
+  unsigned milliseconds = value % 1000;
+  value /= 1000;
+  unsigned seconds = value % 60;
+  value /= 60;
+  unsigned minutes = value % 60;
+  unsigned hours = value / 60;
+  return String::Format("%02u:%02u:%02u.%03u", hours, minutes, seconds,
+                        milliseconds);
+}
+
 bool VTTParser::CollectTimeStamp(VTTScanner& input, double& time_stamp) {
   // Collect a WebVTT timestamp (5.3 WebVTT cue timings and settings parsing.)
   // Steps 1 - 4 - Initial checks, let most significant units be minutes.
@@ -442,11 +455,9 @@ bool VTTParser::CollectTimeStamp(VTTScanner& input, double& time_stamp) {
     return false;
 
   // Steps 18 - 19 - Calculate result.
-  const double kSecondsPerHour = 3600;
-  const double kSecondsPerMinute = 60;
-  const double kSecondsPerMillisecond = 0.001;
-  time_stamp = (value1 * kSecondsPerHour) + (value2 * kSecondsPerMinute) +
-               value3 + (value4 * kSecondsPerMillisecond);
+  time_stamp = (value1 * kMinutesPerHour * kSecondsPerMinute) +
+               (value2 * kSecondsPerMinute) + value3 +
+               (value4 * (1 / kMsPerSecond));
   return true;
 }
 
@@ -550,11 +561,11 @@ void VTTTreeBuilder::ConstructTreeFromToken(Document& document) {
       break;
     }
     case VTTTokenTypes::kTimestampTag: {
-      String characters_string = token_.Characters();
       double parsed_time_stamp;
-      if (VTTParser::CollectTimeStamp(characters_string, parsed_time_stamp))
+      if (VTTParser::CollectTimeStamp(token_.Characters(), parsed_time_stamp)) {
         current_node_->ParserAppendChild(ProcessingInstruction::Create(
-            document, "timestamp", characters_string));
+            document, "timestamp", SerializeTimeStamp(parsed_time_stamp)));
+      }
       break;
     }
     default: