Change WebTimeRange to use doubles instead of floats.

public/platform/WebTimeRange.h

Index: public/platform/WebTimeRange.h
diff --git a/public/platform/WebTimeRange.h b/public/platform/WebTimeRange.h
index 0d5cb1ff71ca8a688bbca05085ec242623ed723a..a37d5b7e97bc6b529ca79a3bfe4549d7c7e56512 100644
--- a/public/platform/WebTimeRange.h
+++ b/public/platform/WebTimeRange.h
@@ -37,10 +37,10 @@ namespace blink {
 
 struct WebTimeRange {
     WebTimeRange() : start(0), end(0) { }
-    WebTimeRange(float s, float e) : start(s), end(e) { }
+    WebTimeRange(double s, double e) : start(s), end(e) { }
 
-    float start;
-    float end;
+    double start;
+    double end;
 };
 
 typedef WebVector<WebTimeRange> WebTimeRanges;