cc: don't scale paint record shaders in fuzzer

Currently we scale all such shaders and rewrite them out as fixed scale
(with a local matrix).  This changes the serialization process and also
adds a matrix where there was not one before.

For the sake of the equality fuzzer, add an option where we don't modify
what we are serializing in this case.

Bug: 898356
Change-Id: I433b921a6e799c2f2d912e6fa61d61bd6a82e2a8
Reviewed-on: https://chromium-review.googlesource.com/c/1298423Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: enne <enne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602553}

cc/paint/paint_op_buffer.h

@@ -164,6 +164,9 @@ class CC_PAINT_EXPORT PaintOp {
     SkColorSpace* color_space = nullptr;
     bool can_use_lcd_text = false;
     bool context_supports_distance_field_text = true;
+    // If true, will calculate a fixed scale for PaintRecord-backed PaintShaders
+    // based on the current canvas scale.  May be turned off for tests.
+    bool scale_paint_record_shaders = true;
     int max_texture_size = 0;
     size_t max_texture_bytes = 0.f;
     SkMatrix original_ctm = SkMatrix::I();

cc/paint/paint_op_buffer_eq_fuzzer.cc

@@ -40,6 +40,12 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   SkNoDrawCanvas canvas(100, 100);
   cc::TestOptionsProvider test_options_provider;
 
+  // This test is trying to verify that serializing and deserializing doesn't
+  // change the results.  Scaling paint shaders and changed them to a fixed
+  // scale when serializing defeats this purpose, so turn that off.
+  test_options_provider.mutable_serialize_options().scale_paint_record_shaders =
+      false;
+
   // Need 4 bytes to be able to read the type/skip.
   if (size < 4)
     return 0;

cc/paint/paint_op_writer.cc

@@ -335,7 +335,8 @@ sk_sp<PaintShader> PaintOpWriter::TransformShaderIfNecessary(
                                         &quality, paint_image_needs_mips);
   }
 
-  if (type == PaintShader::Type::kPaintRecord) {
+  if (type == PaintShader::Type::kPaintRecord &&
+      options_.scale_paint_record_shaders) {
     return original->CreateScaledPaintRecord(ctm, paint_record_post_scale);
   }