[blink] Add IsCrossOriginIsolated getter to blink.h

- Adds a getter to go with the SetIsCrossOriginIsolated function.

We need to be able to access this in content::RenderProcessImpl, in order
to properly set V8 up.

Bug: chromium:923807
Change-Id: I99337ea49537cd6f2b5ebb76f2ceddac38260dbb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2488716Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819202}

third_party/blink/public/web/blink.h

@@ -112,6 +112,7 @@ BLINK_EXPORT void ForceNextDrawingBufferCreationToFailForTest();
 // agents, not both.
 // This is called at most once. This is called earlier than any frame commit.
 BLINK_EXPORT void SetIsCrossOriginIsolated(bool value);
+BLINK_EXPORT bool IsCrossOriginIsolated();
 
 }  // namespace blink
 

third_party/blink/renderer/controller/blink_initializer.cc

@@ -194,6 +194,11 @@ void SetIsCrossOriginIsolated(bool value) {
   Agent::SetIsCrossOriginIsolated(value);
 }
 
+// Function defined in third_party/blink/public/web/blink.h.
+bool IsCrossOriginIsolated() {
+  return Agent::IsCrossOriginIsolated();
+}
+
 void BlinkInitializer::RegisterInterfaces(mojo::BinderMap& binders) {
   ModulesInitializer::RegisterInterfaces(binders);
   Thread* main_thread = Thread::MainThread();