Move SkPdfContext into its own files.

experimental/PdfViewer/inc/SkPdfContext.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.
+ */
+
+#include "SkMatrix.h"
+#include "SkTDStackNester.h"
+#include "SkPdfGraphicsState.h"
+
+class SkPdfAllocator;
+class SkPdfNativeDoc;
+class SkPdfNativeObject;
+
+/** \class SkPdfContext
+ *   The context of the drawing. The document we draw from, the current stack of objects, ...
+ */
+class SkPdfContext {
+public:
+    SkTDStackNester<SkPdfNativeObject*>  fObjectStack;
+    SkTDStackNester<SkPdfGraphicsState>  fStateStack;
+    SkPdfGraphicsState              fGraphicsState;
+    SkPdfNativeDoc*                 fPdfDoc;
+    SkPdfAllocator*                 fTmpPageAllocator;
+    SkMatrix                        fOriginalMatrix;
+
+    SkPdfContext(SkPdfNativeDoc* doc);
+    ~SkPdfContext();
+};