Improve paint op safety around reading SkBlendMode

Bug: 1116243
Change-Id: I9b0541a8bd3c8d4bd43744c1e082f86bfea6249a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2468698Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Cr-Commit-Position: refs/heads/master@{#816714}

cc/paint/paint_op_reader.cc

@@ -265,7 +265,13 @@ void PaintOpReader::Read(PaintFlags* flags) {
   ReadSimple(&flags->color_);
   Read(&flags->width_);
   Read(&flags->miter_limit_);
+
   ReadSimple(&flags->blend_mode_);
+  if (flags->blend_mode_ > static_cast<uint32_t>(SkBlendMode::kLastMode)) {
+    SetInvalid();
+    return;
+  }
+
   ReadSimple(&flags->bitfields_uint_);
 
   ReadFlattenable(&flags->path_effect_);