For readability, refactor some of blink::Editor's methods

This patch does not change any web facing logic.
Only private methods are changed, the public API is untouched.

Renamed methods:
  DispatchCPPEvent -> DispatchClipboardEvent
  TryDHTMLCopy     -> DispatchCopyEvent
  TryDHTMLCut      -> DispatchCutEvent
  TryDHTMLPaste    -> DispatchPasteEvent

These methods now return false upon preventDefault() from JavaScript.
Before this change, only the first method followed this convention.

Bug: 755459
Change-Id: I2b9dd77b0c0cd6a2ad29136e1ec2f9dec7d37622
Reviewed-on: https://chromium-review.googlesource.com/810806Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Hugo Holgersson <hugoh@vewd.com>
Cr-Commit-Position: refs/heads/master@{#523810}

third_party/WebKit/Source/core/editing/Editor.h

@@ -339,17 +339,18 @@ class CORE_EXPORT Editor final : public GarbageCollectedFinalized<Editor> {
 
   bool CanDeleteRange(const EphemeralRange&) const;
 
-  bool TryDHTMLCopy();
-  bool TryDHTMLCut();
-  bool TryDHTMLPaste(PasteMode);
+  // Returns true if Editor should continue with default processing.
+  bool DispatchCopyEvent();
+  bool DispatchCutEvent();
+  bool DispatchPasteEvent(PasteMode);
+  bool DispatchClipboardEvent(const AtomicString&,
+                              DataTransferAccessPolicy,
+                              PasteMode = kAllMimeTypes);
 
   bool CanSmartReplaceWithPasteboard(Pasteboard*);
   void PasteAsPlainTextWithPasteboard(Pasteboard*);
   void PasteWithPasteboard(Pasteboard*);
   void WriteSelectionToPasteboard();
-  bool DispatchCPPEvent(const AtomicString&,
-                        DataTransferAccessPolicy,
-                        PasteMode = kAllMimeTypes);
 
   void RevealSelectionAfterEditingOperation(
       const ScrollAlignment& = ScrollAlignment::kAlignCenterIfNeeded);