[PDF] Fix memory hungry inefficiency in pdf resource tracking.

[PDF] Fix memory hungry inefficiency in pdf resource tracking.

When moving the content of a device into a PDF object like SkPDFFormXObject
or SkPDFShader does, we only need the top level resources in the new object's
resource list, not the recursive set of objects.  Otherwise, when you
put a form on a form on form, etc, references to the objects multiply.

This fixed http://crbug.com/117321

Review URL: https://codereview.appspot.com/5796048

git-svn-id: http://skia.googlecode.com/svn/trunk@3360 2bbb7eff-a529-9590-31e7-b0007b416f81