Introduce InspectorIdentifiers<> and use it to assign/lookup LocalFrame and DocumentLoader

Source/core/inspector/InspectorPageAgent.h

Index: Source/core/inspector/InspectorPageAgent.h
diff --git a/Source/core/inspector/InspectorPageAgent.h b/Source/core/inspector/InspectorPageAgent.h
index 38550c4090b21ecdf3cd09b1fd036d7e3d8670f7..5d009a8368c6e2e27b52bb82a6cdf44422d7a81d 100644
--- a/Source/core/inspector/InspectorPageAgent.h
+++ b/Source/core/inspector/InspectorPageAgent.h
@@ -107,7 +107,6 @@ public:
     void didCommitLoad(LocalFrame*, DocumentLoader*);
     void frameAttachedToParent(LocalFrame*);
     void frameDetachedFromParent(LocalFrame*);
-    void loaderDetachedFromFrame(DocumentLoader*);
     void frameStartedLoading(LocalFrame*);
     void frameStoppedLoading(LocalFrame*);
     void frameScheduledNavigation(LocalFrame*, double delay);
@@ -125,17 +124,13 @@ public:
     void discardAgent() override;
 
     // Cross-agents API
+    static DocumentLoader* assertDocumentLoader(ErrorString*, LocalFrame*);
+    LocalFrame* frameForId(const String& frameId);
+    LocalFrame* assertFrame(ErrorString*, const String& frameId);
     FrameHost* frameHost();
     LocalFrame* inspectedFrame() const { return m_inspectedFrame.get(); }
-    String createIdentifier();
-    LocalFrame* frameForId(const String& frameId);
-    String frameId(LocalFrame*);
-    bool hasIdForFrame(LocalFrame*) const;
-    String loaderId(DocumentLoader*);
     LocalFrame* findFrameWithSecurityOrigin(const String& originRawString);
-    LocalFrame* assertFrame(ErrorString*, const String& frameId);
     bool screencastEnabled();
-    static DocumentLoader* assertDocumentLoader(ErrorString*, LocalFrame*);
     InspectorResourceContentLoader* resourceContentLoader() { return m_inspectorResourceContentLoader.get(); }
 
     DECLARE_VIRTUAL_TRACE();
@@ -159,9 +154,6 @@ private:
     long m_lastScriptIdentifier;
     String m_pendingScriptToEvaluateOnLoadOnce;
     String m_scriptToEvaluateOnLoadOnce;
-    HashMap<LocalFrame*, String> m_frameToIdentifier;
-    HashMap<String, LocalFrame*> m_identifierToFrame;
-    HashMap<DocumentLoader*, String> m_loaderToIdentifier;
     bool m_enabled;
     bool m_reloading;