Don't find(':') twice in WebVTTParser::collectMetadataHeader

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

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 226 matching lines @@
         return false;
 
     return true;
 }
 
 void WebVTTParser::collectMetadataHeader(const String& line)
 {
     // WebVTT header parsing (WebVTT parser algorithm step 12)
     DEFINE_STATIC_LOCAL(const AtomicString, regionHeaderName, ("Region", AtomicString::ConstructFromLiteral));
 
+    // The only currently supported header is the "Region" header.
+    if (!RuntimeEnabledFeatures::webVTTRegionsEnabled())
+        return;
+
     // Step 12.4 If line contains the character ":" (A U+003A COLON), then set metadata's
     // name to the substring of line before the first ":" character and
     // metadata's value to the substring after this character.
-    if (!RuntimeEnabledFeatures::webVTTRegionsEnabled() || !line.contains(":"))
+    unsigned colonPosition = line.find(':');
+    if (colonPosition == kNotFound)
         return;
 
-    unsigned colonPosition = line.find(":");
     String headerName = line.substring(0, colonPosition);
 
     // Steps 12.5 If metadata's name equals "Region":
     if (headerName == regionHeaderName) {
         String headerValue = line.substring(colonPosition + 1);
         // Steps 12.5.1 - 12.5.11 Region creation: Let region be a new text track region [...]
         createNewRegion(headerValue);
     }
 }
 
@@ skipping 301 matching lines @@
 }
 
 void WebVTTParser::skipWhiteSpace(const String& line, unsigned* position)
 {
     while (*position < line.length() && isASpace(line[*position]))
         (*position)++;
 }
 
 }