Fuzz PDF, N32, and Null Canvases

run `fuzz --type pdf_canvas` or `fuzz --type null_canvas` or
`fuzz --type n32_canvas`

Change-Id: Id70179d5578ed1e67006aef7823bf75fc1d7a4a6
Reviewed-on: https://skia-review.googlesource.com/8418
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index e8d24db..b23277c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1306,6 +1306,7 @@
   test_app("fuzz") {
     sources = [
       "fuzz/FilterFuzz.cpp",
+      "fuzz/FuzzCanvas.cpp",
       "fuzz/FuzzDrawFunctions.cpp",
       "fuzz/FuzzGradients.cpp",
       "fuzz/FuzzParsePath.cpp",