store MetafileSkiaWrapper in plugin instead of canvas

content/renderer/pepper/pepper_plugin_instance_impl.h

Index: content/renderer/pepper/pepper_plugin_instance_impl.h
diff --git a/content/renderer/pepper/pepper_plugin_instance_impl.h b/content/renderer/pepper/pepper_plugin_instance_impl.h
index dade2ee2e63503878d7917311a4de7a5f33ce407..49aa201c6df9d75fa6dd2463cfdcb625f3516511 100644
--- a/content/renderer/pepper/pepper_plugin_instance_impl.h
+++ b/content/renderer/pepper/pepper_plugin_instance_impl.h
@@ -98,6 +98,10 @@ struct PPP_Instance_Combined;
 class ScopedPPVar;
 }
 
+namespace printing {
+class MetafileSkiaWrapper;
+}
+
 namespace content {
 
 class ContentDecryptorDelegate;
@@ -645,7 +649,8 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // best format to use. Returns false if the plugin does not support any
   // print format that we can handle (we can handle only PDF).
   bool GetPreferredPrintOutputFormat(PP_PrintOutputFormat_Dev* format);
-  bool PrintPDFOutput(PP_Resource print_output, blink::WebCanvas* canvas);
+  bool PrintPDFOutput(PP_Resource print_output,
+                      printing::MetafileSkiaWrapper* wrapper);
 
   // Updates the layer for compositing. This creates a layer and attaches to the
   // container if:
@@ -660,8 +665,7 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
 
   // Internal helper function for PrintPage().
   void PrintPageHelper(PP_PrintPageNumberRange_Dev* page_ranges,
-                       int num_ranges,
-                       blink::WebCanvas* canvas);
+                       int num_ranges, printing::MetafileSkiaWrapper* wrapper);
 
   void DoSetCursor(blink::WebCursorInfo* cursor);
 
@@ -835,13 +839,13 @@ class CONTENT_EXPORT PepperPluginInstanceImpl
   // and Win, the entire document goes into one metafile.  However, when users
   // print only a subset of all the pages, it is impossible to know if a call
   // to PrintPage() is the last call. Thus in PrintPage(), just store the page
-  // number in |ranges_|. The hack is in PrintEnd(), where a valid |canvas_|
+  // number in |ranges_|. The hack is in PrintEnd(), where a valid
+  // |metafile_wrapper_|

[bbudge, 2016/11/17 22:37:00]

nit: formatting is a little hard to read here.

   // is preserved in PrintWebViewHelper::PrintPages. This makes it possible
   // to generate the entire PDF given the variables below:
   //
-  // The most recently used WebCanvas to be used in printEnd(). Caller must
-  // ensure that it remains valid until that point.
-  blink::WebCanvas* canvas_;
+  // The most recently used metafile wrapper from the most recently used canvas
+  sk_sp<printing::MetafileSkiaWrapper> metafile_wrapper_;

[Lei Zhang, 2016/11/18 02:25:53]

So this is slightly problematic as-is because it always pulls in printing as a
dependency, and there are build configs where printing is turned off. I'll see
if we can ifdef this...

   // An array of page ranges.
   std::vector<PP_PrintPageNumberRange_Dev> ranges_;