SkPDF: add basic metadata support

include/core/SkTArray.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTArray_DEFINED
 #define SkTArray_DEFINED
 
@@ skipping 176 matching lines @@
     /**
      * Version of above that uses a copy constructor to initialize the new item
      */
     T& push_back(const T& t) {
         T* newT = reinterpret_cast<T*>(this->push_back_raw(1));
         new (newT) T(t);
         return *newT;
     }
 
     /**
+     *  Construct a new T at the back of this array.
+     */
+    template<class... Args> T& emplace_back(Args&&... args) {
+        T* newT = reinterpret_cast<T*>(this->push_back_raw(1));
+        return *new (newT) T(skstd::forward<Args>(args)...);
+    }
+
+    /**
      * Allocates n more default-initialized T values, and returns the address of
      * the start of that new range. Note: this address is only valid until the
      * next API call made on the array that might add or remove elements.
      */
     T* push_back_n(int n) {
         SkASSERT(n >= 0);
         T* newTs = reinterpret_cast<T*>(this->push_back_raw(n));
         for (int i = 0; i < n; ++i) {
             new (newTs + i) T;
         }
@@ skipping 334 matching lines @@
     SkSTArray& operator= (const INHERITED& array) {
         INHERITED::operator=(array);
         return *this;
     }
 
 private:
     SkAlignedSTStorage<N,T> fStorage;
 };
 
 #endif