Move document.write evaluation after standard preloads

third_party/WebKit/Source/core/html/parser/HTMLDocumentParser.cpp

 /*
  * Copyright (C) 2010 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 303 matching lines @@
                 ASSERT(token.type() == HTMLToken::TokenType::Character);
                 m_queuedDocumentWriteScripts.append(token.data());
             }
         }
     } else {
         // We can safely assume that there are no queued preloads request after
         // the document element is available, as we empty the queue immediately
         // after the document element is created in documentElementAvailable().
         ASSERT(m_queuedPreloads.isEmpty());
         ASSERT(m_queuedDocumentWriteScripts.isEmpty());
+        // Loop through the chunks to generate preloads before any
+        // document.write script evaluation takes place. Preloading these
+        // scripts is valuable and comparably cheap, while evaluating JS can be
+        // expensive.
+        for (auto& chunk : pendingChunks) {
+            m_preloader->takeAndPreload(chunk->preloads);
+        }
         for (auto& chunk : pendingChunks) {
             for (auto& index : chunk->likelyDocumentWriteScriptIndices) {
                 const CompactHTMLToken& token = chunk->tokens->at(index);
                 ASSERT(token.type() == HTMLToken::TokenType::Character);
                 evaluateAndPreloadScriptForDocumentWrite(token.data());
             }
-            m_preloader->takeAndPreload(chunk->preloads);
         }
     }
 
     for (auto& chunk : pendingChunks)
         m_speculations.append(std::move(chunk));
 
     if (!isWaitingForScripts() && !isScheduledForResume()) {
         if (m_tasksWereSuspended)
             m_parserScheduler->forceResumeAfterYield();
         else
@@ skipping 727 matching lines @@
     DecodedDataDocumentParser::setDecoder(std::move(decoder));
 
     if (m_haveBackgroundParser)
         postTaskToLookaheadParser(crossThreadBind(&BackgroundHTMLParser::setDecoder, m_backgroundParser, passed(takeDecoder())));
 }
 
 void HTMLDocumentParser::documentElementAvailable()
 {
     TRACE_EVENT0("blink,loader", "HTMLDocumentParser::documentElementAvailable");
     DCHECK(document()->documentElement());
+    if (!m_queuedPreloads.isEmpty())
+        m_preloader->takeAndPreload(m_queuedPreloads);
+
     for (const String& scriptSource : m_queuedDocumentWriteScripts) {
         evaluateAndPreloadScriptForDocumentWrite(scriptSource);
     }
 
     m_queuedDocumentWriteScripts.clear();
-    if (!m_queuedPreloads.isEmpty())
-        m_preloader->takeAndPreload(m_queuedPreloads);
 }
 
 std::unique_ptr<HTMLPreloadScanner> HTMLDocumentParser::createPreloadScanner()
 {
     return HTMLPreloadScanner::create(
         m_options,
         document()->url(),
         CachedDocumentParameters::create(document()),
         MediaValuesCached::MediaValuesCachedData(*document()));
 }
@@ skipping 51 matching lines @@
         (*closure)();
         return;
     case Asynchronous:
         m_loadingTaskRunner->postTask(BLINK_FROM_HERE, std::move(closure));
         return;
     }
     NOTREACHED();
 }
 
 } // namespace blink