SkPDF: add basic metadata support

include/core/SkDocument.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDocument_DEFINED
 #define SkDocument_DEFINED
 
 #include "SkBitmap.h"
 #include "SkPicture.h"
 #include "SkRect.h"
 #include "SkRefCnt.h"
+#include "SkString.h"
+#include "SkTime.h"
 
 class SkCanvas;
 class SkWStream;
 
 /** SK_ScalarDefaultDPI is 72 DPI.
 */
 #define SK_ScalarDefaultRasterDPI           72.0f
 
 /**
  *  High-level API for creating a document-based canvas. To use..
@@ skipping 72 matching lines @@
      *  Returns true on success or false on failure.
      */
     bool close();
 
     /**
      *  Call abort() to stop producing the document immediately.
      *  The stream output must be ignored, and should not be trusted.
      */
     void abort();
 
+    /**
+     *  Set the document's metadata, if supported by the document
+     *  type.  The creationDate and modifiedDate parameters can be
+     *  nullptr.  For example:
+     *
+     *  SkDocument* make_doc(SkWStream* output) {
+     *      SkTArray<SkDocument::Attribute> info;
+     *      info.emplace_back(SkString("Title"), SkString("..."));
+     *      info.emplace_back(SkString("Author"), SkString("..."));
+     *      info.emplace_back(SkString("Subject"), SkString("..."));
+     *      info.emplace_back(SkString("Keywords"), SkString("..."));
+     *      info.emplace_back(SkString("Creator"), SkString("..."));
+     *      SkTime::DateTime now;
+     *      SkTime::GetDateTime(&now);
+     *      SkDocument* doc = SkDocument::CreatePDF(output);
+     *      doc->setMetadata(info, &now, &now);
+     *      return doc;
+     *  }
+     */
+    struct Attribute {
+        SkString key, value;

[reed1, 2015/09/23 10:14:47]

following skia fNaming fConvention?

[hal.canary, 2015/09/23 12:42:43]

Done.

+        Attribute(const SkString& k, const SkString& v) : key(k), value(v) {}
+    };
+    virtual void setMetadata(const SkTArray<SkDocument::Attribute>&,
+                             const SkTime::DateTime* /* creationDate */,
+                             const SkTime::DateTime* /* modifiedDate */) {}
+
 protected:
     SkDocument(SkWStream*, void (*)(SkWStream*, bool aborted));
 
     // note: subclasses must call close() in their destructor, as the base class
     // cannot do this for them.
     virtual ~SkDocument();
 
     virtual SkCanvas* onBeginPage(SkScalar width, SkScalar height,
                                   const SkRect& content) = 0;
     virtual void onEndPage() = 0;
@@ skipping 12 matching lines @@
 
 private:
     SkWStream* fStream;
     void       (*fDoneProc)(SkWStream*, bool aborted);
     State      fState;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif