Revert of DevTools: remove dependency of most agents on InspectorPageAgent

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 bd031060a5fd1d7e1eda28de25fbeeb0e7feeb19..5d009a8368c6e2e27b52bb82a6cdf44422d7a81d 100644
--- a/Source/core/inspector/InspectorPageAgent.h
+++ b/Source/core/inspector/InspectorPageAgent.h
@@ -124,6 +124,12 @@
     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(); }
+    LocalFrame* findFrameWithSecurityOrigin(const String& originRawString);
     bool screencastEnabled();
     InspectorResourceContentLoader* resourceContentLoader() { return m_inspectorResourceContentLoader.get(); }
 
@@ -136,7 +142,6 @@
 
     void finishReload();
     void getResourceContentAfterResourcesContentLoaded(const String& frameId, const String& url, PassRefPtrWillBeRawPtr<GetResourceContentCallback>);
-    LocalFrame* assertFrame(ErrorString*, const String& frameId);
 
     static bool dataContent(const char* data, unsigned size, const String& textEncodingName, bool withBase64Encode, String* result);