Fix TimeRanges::nearest() to actually calculate nearest time.

The existing implementation instead couldn't decide if it wanted to
calculate the nearest time or how close a given time was to a range.

The new implementation follows the HTML spec for TimeRanges where
nearest() returns a time within the range closest to the desired
time. Equidistant matches are resolved by distance from the current
time.

BUG=412562
TEST=new unittest.

Review URL: https://codereview.chromium.org/559993004

git-svn-id: svn://svn.chromium.org/blink/trunk@181859 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

@@ -1992,7 +1992,7 @@ void HTMLMediaElement::seek(double time)
         m_seeking = false;
         return;
     }
-    time = seekableRanges->nearest(time);
+    time = seekableRanges->nearest(time, now);
 
     if (m_playing) {
         if (m_lastSeekTime < now)

third_party/WebKit/Source/core/html/TimeRanges.cpp

@@ -182,21 +182,33 @@ bool TimeRanges::contain(double time) const
     return false;
 }
 
-double TimeRanges::nearest(double time) const
+double TimeRanges::nearest(double newPlaybackPosition, double currentPlaybackPosition) const
 {
-    double closest = 0;
     unsigned count = length();
+    double bestMatch = 0;
+    double bestDelta = std::numeric_limits<double>::infinity();
     for (unsigned ndx = 0; ndx < count; ndx++) {
         double startTime = start(ndx, IGNORE_EXCEPTION);
         double endTime = end(ndx, IGNORE_EXCEPTION);
-        if (time >= startTime && time <= endTime)
-            return time;
-        if (fabs(startTime - time) < closest)
-            closest = fabs(startTime - time);
-        else if (fabs(endTime - time) < closest)
-            closest = fabs(endTime - time);
+        if (newPlaybackPosition >= startTime && newPlaybackPosition <= endTime)
+            return newPlaybackPosition;
+
+        double delta, match;
+        if (newPlaybackPosition < startTime) {
+            delta = startTime - newPlaybackPosition;
+            match = startTime;
+        } else {
+            delta = newPlaybackPosition - endTime;
+            match = endTime;
+        }
+
+        if (delta < bestDelta || (delta == bestDelta
+            && std::abs(currentPlaybackPosition - match) < std::abs(currentPlaybackPosition - bestMatch))) {
+            bestDelta = delta;
+            bestMatch = match;
+        }
     }
-    return closest;
+    return bestMatch;
 }
 
 void TimeRanges::trace(Visitor* visitor)

third_party/WebKit/Source/core/html/TimeRanges.h

@@ -109,7 +109,7 @@ public:
 
     bool contain(double time) const;
 
-    double nearest(double time) const;
+    double nearest(double newPlaybackPosition, double currentPlaybackPosition) const;
 
     void trace(Visitor*);
 

third_party/WebKit/Source/core/html/TimeRangesTest.cpp

@@ -298,3 +298,23 @@ TEST(TimeRanges, IntersectWith_Gaps3)
     ASSERT_RANGE("{ [1,2) [4,5) [6,7) [8,9) }", rangesA);
     ASSERT_RANGE("{ [1,5) [6,9) }", rangesB);
 }
+
+TEST(TimeRanges, Nearest)
+{
+    RefPtrWillBeRawPtr<TimeRanges> ranges = TimeRanges::create();
+    ranges->add(0, 2);
+    ranges->add(5, 7);
+
+    ASSERT_EQ(0, ranges->nearest(0, 0));
+    ASSERT_EQ(1, ranges->nearest(1, 0));
+    ASSERT_EQ(2, ranges->nearest(2, 0));
+    ASSERT_EQ(2, ranges->nearest(3, 0));
+    ASSERT_EQ(5, ranges->nearest(4, 0));
+    ASSERT_EQ(5, ranges->nearest(5, 0));
+    ASSERT_EQ(7, ranges->nearest(8, 0));
+
+    ranges->add(9, 11);
+    ASSERT_EQ(7, ranges->nearest(8, 6));
+    ASSERT_EQ(7, ranges->nearest(8, 8));
+    ASSERT_EQ(9, ranges->nearest(8, 10));
+}