Media Controls: Do not show cached timeline segment

The modern media controls should not show what has been previously
cached on the left hand side of the play head. This pins the segment to
the zero position so it always is filled in.

BUG=827539

Change-Id: I97f5f06b7e349faf163667d2b19ef8930e0b13c7
Reviewed-on: https://chromium-review.googlesource.com/994180Reviewed-by: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548099}

third_party/WebKit/Source/modules/media_controls/elements/MediaControlTimelineElement.cpp

@@ -201,6 +201,15 @@ void MediaControlTimelineElement::RenderBarSegments() {
   }
 
   double current_position = current_time / duration;
+  MediaControlSliderElement::Position before_segment(0, 0);
+  MediaControlSliderElement::Position after_segment(0, 0);
+
+  // The before segment (i.e. what has been played) should be purely be based on
+  // the current time in the modern controls.
+  if (MediaControlsImpl::IsModern())
+    before_segment.width = current_position;
+
+  // Calculate the size of the after segment (i.e. what has been buffered).
   for (unsigned i = 0; i < buffered_time_ranges->length(); ++i) {
     float start = buffered_time_ranges->start(i, ASSERT_NO_EXCEPTION);
     float end = buffered_time_ranges->end(i, ASSERT_NO_EXCEPTION);
@@ -221,34 +230,31 @@ void MediaControlTimelineElement::RenderBarSegments() {
     double end_position = end / duration;
 
     if (MediaControlsImpl::IsModern()) {
-      // Draw highlight to show what we have played.
-      SetBeforeSegmentPosition(MediaControlSliderElement::Position(
-          start_position, current_position - start_position));
-
       // Draw dark grey highlight to show what we have loaded.
-      SetAfterSegmentPosition(MediaControlSliderElement::Position(
-          current_position, end_position - current_position));
+      after_segment.left = current_position;
+      after_segment.width = end_position - current_position;
     } else {
       // Draw highlight to show what we have played.
       if (current_position > start_position) {
-        SetAfterSegmentPosition(MediaControlSliderElement::Position(
-            start_position, current_position - start_position));
+        after_segment.left = start_position;
+        after_segment.width = current_position - start_position;
       }
 
       // Draw dark grey highlight to show what we have loaded.
       if (end_position > current_position) {
-        SetBeforeSegmentPosition(MediaControlSliderElement::Position(
-            current_position, end_position - current_position));
+        before_segment.left = current_position;
+        before_segment.width = end_position - current_position;
       }
     }
 
-    // Return since we've drawn the only buffered range we're going to draw.
-    return;
+    // Break out of the loop since we've drawn the only buffered range
+    // we're going to draw.
+    break;
   }
 
-  // Reset the widths to hide the segments.
-  SetBeforeSegmentPosition(MediaControlSliderElement::Position(0, 0));
-  SetAfterSegmentPosition(MediaControlSliderElement::Position(0, 0));
+  // Update the positions of the segments.
+  SetBeforeSegmentPosition(before_segment);
+  SetAfterSegmentPosition(after_segment);
 }
 
 void MediaControlTimelineElement::Trace(blink::Visitor* visitor) {