Refactor the way singleton-style resources are exposed via PPB_Instance

ppapi/thunk/enter.h

Index: ppapi/thunk/enter.h
diff --git a/ppapi/thunk/enter.h b/ppapi/thunk/enter.h
index 276f0457647d07d08f367cbced88430fdf781c3c..9c43a6d76bd5481c53daef6c53bc16e04e629621 100644
--- a/ppapi/thunk/enter.h
+++ b/ppapi/thunk/enter.h
@@ -245,6 +245,46 @@ class PPAPI_THUNK_EXPORT EnterInstanceNoLock
   PPB_Instance_API* functions_;
 };
 
+// EnterInstanceAPI ------------------------------------------------------------
+
+template<typename ApiT, bool lock_on_entry = true>
+class PPAPI_THUNK_EXPORT EnterInstanceAPI
+    : public subtle::EnterBase,
+      public subtle::LockOnEntry<lock_on_entry> {
+ public:
+  EnterInstanceAPI(PP_Instance instance) : EnterBase() {

[dmichael (off chromium), 2012/11/21 17:26:26]

nit: explicit

[raymes, 2012/11/21 20:59:10]

Done.

+    functions_ = NULL;

[dmichael (off chromium), 2012/11/21 17:26:26]

nit: Why not initialize this in the initializer list?

[raymes, 2012/11/21 20:59:10]

Done.

+    PPB_Instance_API* ppb_instance =
+        PpapiGlobals::Get()->GetInstanceAPI(instance);
+    if (ppb_instance) {
+      Resource* resource =
+          ppb_instance->GetSingletonResource(instance,
+                                             ApiT::kSingletonResourceID);
+      if (resource)
+        functions_ = resource->GetAs<ApiT>();
+    }
+    SetStateForFunctionError(instance, functions_, true);
+  }
+  ~EnterInstanceAPI() {}
+
+  bool succeeded() const { return !!functions_; }
+  bool failed() const { return !functions_; }
+
+  ApiT* functions() { return functions_; }

[dmichael (off chromium), 2012/11/21 17:26:26]

I'm noticing we don't do this in EnterInstance either, but that should probably
be "const ApiT* functions() const"
(unless that's getting too crazy with const)

[raymes, 2012/11/21 20:59:10]

As discussed, we can't return const ApiT* because it would mean all the API
methods have to be const. But I made functions() const.

+
+ private:
+  ApiT* functions_;
+};
+
+template<typename ApiT>
+class PPAPI_THUNK_EXPORT EnterInstanceAPINoLock
+    : public EnterInstanceAPI<ApiT, false> {
+ public:
+  EnterInstanceAPINoLock(PP_Instance instance)
+      : EnterInstanceAPI<ApiT, false>(instance) {
+  }
+};
+
 // EnterResourceCreation -------------------------------------------------------
 
 class PPAPI_THUNK_EXPORT EnterResourceCreation