Move the writing of the MHTML footer to the browser process.

third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h

Index: third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h
diff --git a/third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h b/third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h
index c538d24ea77f782ad44c205bd3ecf02df7218935..362fbd0f4812641ed7756d6b4b3845f5185e05bc 100644
--- a/third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h
+++ b/third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h
@@ -78,13 +78,14 @@ class PLATFORM_EXPORT MHTMLArchive final
                                 const SerializedResource&,
                                 Vector<char>& outputBuffer);
 
-  // Generates an MHTML footer and appends it to |outputBuffer|.
+  // Generates an MHTML footer and appends it to |outputBuffer| for testing
+  // purposes.
   //
   // Same |boundary| needs to used for all generateMHTMLHeader and
   // generateMHTMLPart and generateMHTMLFooter calls that belong to the same
   // MHTML document (see also rfc1341, section 7.2.1, "boundary" description).
-  static void generateMHTMLFooter(const String& boundary,
-                                  Vector<char>& outputBuffer);
+  static void generateMHTMLFooterForTesting(const String& boundary,
+                                            Vector<char>& outputBuffer);
 
   typedef HeapHashMap<String, Member<ArchiveResource>> SubArchiveResources;