ServiceWorker: Make a way to retrieve a service worker version id (Blink)

Source/core/fetch/ResourceFetcher.cpp

Index: Source/core/fetch/ResourceFetcher.cpp
diff --git a/Source/core/fetch/ResourceFetcher.cpp b/Source/core/fetch/ResourceFetcher.cpp
index e6d13535757fe6171ad088c3e2218dda1bcc5d07..c5fe50271818ad67cbd39ba1312ba5dbab4c1eec 100644
--- a/Source/core/fetch/ResourceFetcher.cpp
+++ b/Source/core/fetch/ResourceFetcher.cpp
@@ -624,6 +624,20 @@ bool ResourceFetcher::isControlledByServiceWorker() const
     return localFrame->loader().client()->isControlledByServiceWorker(*m_documentLoader);
 }
 
+int64_t ResourceFetcher::serviceWorkerID() const
+{
+    LocalFrame* localFrame = frame();
+    if (!localFrame)
+        return -1;

[Mike West, 2014/10/28 08:09:24]

Why are you using -1 as the invalid value? Why not 0? 0 makes comparisons
simpler to understand, and would allow you to make this a `uint64_t` instead.
That would be less prone to breakage.

[nhiroki, 2014/10/28 08:34:01]

This seviceWorkerID is corresponding to the ServiceWorkerVersionId in Chromium
and it's zero-based number (-1 is used as an invalid number[1]).

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/content/common/ser...

+    if (m_documentLoader)
+        return localFrame->loader().client()->serviceWorkerID(*m_documentLoader);
+    // m_documentLoader is null while loading resources from the imported HTML.
+    // In such cases a service worker ID could be retrieved from the document
+    // loader of the frame.
+    ASSERT(localFrame->loader().documentLoader());
+    return localFrame->loader().client()->serviceWorkerID(*localFrame->loader().documentLoader());
+}
+
 bool ResourceFetcher::shouldLoadNewResource(Resource::Type type) const
 {
     if (!frame())