Make the v8 Isolate used in the proxy resolver explicit.

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index ec09bd887bae4766021b95e8e1e5391999dbe5fc..699d347e5cb0f4187c474eb86d35b7825a823059 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -64,6 +64,10 @@ namespace policy {
 class PolicyService;
 }  // namespace policy
 
+namespace v8 {
+class Isolate;
+}  // namespace v8
+
 // Contains state associated with, initialized and cleaned up on, and
 // primarily used on, the IO thread.
 //
@@ -165,6 +169,8 @@ class IOThread : public content::BrowserThreadDelegate {
     // main frame load fails with a DNS error in order to provide more useful
     // information to the renderer so it can show a more specific error page.
     scoped_ptr<chrome_browser_net::DnsProbeService> dns_probe_service;
+    // The v8 default Isolate for the main thread.

[jochen (gone - plz use gerrit), 2013/01/18 13:29:07]

the comment is a bit misleading, since we'll use it on the IO thread.

isn't it also the case that it's only safe to use this isolate from one thread
at a time, so whoever uses it needs to make sure to lock v8 user a V8::Locker?

[Sven Panne, 2013/01/18 14:27:33]

OK, it is v8's default Isolate, retrieved *from* the main thread. I'll change
that...
It's a bit the other way round: We actually need the Isolate in the (Un)Locker
constructor to allow any usage of it in the current thread.

V8's API is a bit ugly regarding this: Compared to Java's JNI, we don't really
distinguish between JavaVM and JNIEnv, and we mix Attach/DetachCurrentThread
with the actual locking.

Isolates have been an afterthought and cleaning all this mess up is a long,
ongoing task, where this current CL is a tiny step...

+    v8::Isolate* v8_default_isolate;
   };
 
   // |net_log| must either outlive the IOThread or be NULL.
@@ -300,6 +306,8 @@ class IOThread : public content::BrowserThreadDelegate {
 
   base::WeakPtrFactory<IOThread> weak_factory_;
 
+  v8::Isolate* v8_default_isolate_;
+
   DISALLOW_COPY_AND_ASSIGN(IOThread);
 };