Unroll PaintFlags dtor to investigate crashes

Bug: 790915
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I3f1455a61d27e59ac2b5dc49da049044119b6245
Reviewed-on: https://chromium-review.googlesource.com/990236
Commit-Queue: enne <enne@chromium.org>
Reviewed-by: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547829}

cc/paint/paint_flags.cc

@@ -36,7 +36,21 @@ PaintFlags::PaintFlags(const PaintFlags& flags) = default;
 
 PaintFlags::PaintFlags(PaintFlags&& other) = default;
 
-PaintFlags::~PaintFlags() = default;
+PaintFlags::~PaintFlags() {
+  // TODO(enne): non-default dtor to investigate http://crbug.com/790915
+
+  // Sanity check accessing this object doesn't crash.
+  CHECK_NE(blend_mode_, static_cast<uint32_t>(SkBlendMode::kLastMode) + 100);
+
+  // Free refcounted objects one by one.
+  typeface_.reset();
+  path_effect_.reset();
+  shader_.reset();
+  mask_filter_.reset();
+  color_filter_.reset();
+  draw_looper_.reset();
+  image_filter_.reset();
+}
 
 PaintFlags& PaintFlags::operator=(const PaintFlags& other) = default;