Revert "Revert "Revert "Reland PerformanceOverlayLayer golden test (f…

…lutter#7863)" (flutter#7895)" (flutter#7911)" (flutter#7916)

This breaks the Linux build with:
```
[ RUN      ] PerformanceOverlayLayer.Gold
../../flutter/flow/layers/performance_overlay_layer_unittests.cc:70: Failure
Value of: golden_data != nullptr
  Actual: false
Expected: true
Golden file not found: "/b/s/w/ir/k/src/flutter/testing/resources"/performance_overlay_gold.png.
Please either set --golden-dir, or make sure that the unit test is run from the right directory (e.g., flutter/engine/src).
```

This reverts commit 3f0ce76.

ci/licenses_golden/licenses_flutter

@@ -88,7 +88,6 @@ FILE: ../../../flutter/flow/layers/opacity_layer.cc
 FILE: ../../../flutter/flow/layers/opacity_layer.h
 FILE: ../../../flutter/flow/layers/performance_overlay_layer.cc
 FILE: ../../../flutter/flow/layers/performance_overlay_layer.h
-FILE: ../../../flutter/flow/layers/performance_overlay_layer_unittests.cc
 FILE: ../../../flutter/flow/layers/physical_shape_layer.cc
 FILE: ../../../flutter/flow/layers/physical_shape_layer.h
 FILE: ../../../flutter/flow/layers/picture_layer.cc
@@ -728,13 +727,9 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ====================================================================================================
 
 ====================================================================================================
-LIBRARY: engine
 LIBRARY: txt
 ORIGIN: ../../../flutter/third_party/txt/LICENSE
 TYPE: LicenseType.apache
-FILE: ../../../flutter/flow/flow_run_all_unittests.cc
-FILE: ../../../flutter/flow/flow_test_utils.cc
-FILE: ../../../flutter/flow/flow_test_utils.h
 FILE: ../../../flutter/third_party/txt/benchmarks/paint_record_benchmarks.cc
 FILE: ../../../flutter/third_party/txt/benchmarks/paragraph_benchmarks.cc
 FILE: ../../../flutter/third_party/txt/benchmarks/paragraph_builder_benchmarks.cc

flow/BUILD.gn

@@ -93,18 +93,13 @@ executable("flow_unittests") {
   testonly = true
 
   sources = [
-    "flow_run_all_unittests.cc",
-    "flow_test_utils.h",
-    "flow_test_utils.cc",
     "matrix_decomposition_unittests.cc",
     "raster_cache_unittests.cc",
-    "layers/performance_overlay_layer_unittests.cc",
   ]
 
   deps = [
     ":flow",
-    "$flutter_root/fml",
-    "//third_party/googletest:gtest",
+    "$flutter_root/testing",
     "//third_party/dart/runtime:libdart_jit",  # for tracing
     "//third_party/skia",
   ]

flow/layers/performance_overlay_layer.cc

@@ -15,12 +15,8 @@ namespace {
 void DrawStatisticsText(SkCanvas& canvas,
                         const std::string& string,
                         int x,
-                        int y,
-                        const std::string& font_path) {
+                        int y) {
   SkFont font;
-  if (font_path != "") {
-    font = SkFont(SkTypeface::MakeFromFile(font_path.c_str()));
-  }
   font.setSize(15);
   font.setLinearMetrics(false);
   SkPaint paint;
@@ -37,8 +33,7 @@ void VisualizeStopWatch(SkCanvas& canvas,
                         SkScalar height,
                         bool show_graph,
                         bool show_labels,
-                        const std::string& label_prefix,
-                        const std::string& font_path) {
+                        const std::string& label_prefix) {
   const int label_x = 8;    // distance from x
   const int label_y = -10;  // distance from y+height
 
@@ -56,20 +51,14 @@ void VisualizeStopWatch(SkCanvas& canvas,
     stream << label_prefix << "  "
            << "max " << max_ms_per_frame << " ms/frame, "
            << "avg " << average_ms_per_frame << " ms/frame";
-    DrawStatisticsText(canvas, stream.str(), x + label_x, y + height + label_y,
-                       font_path);
+    DrawStatisticsText(canvas, stream.str(), x + label_x, y + height + label_y);
   }
 }
 
 }  // namespace
 
-PerformanceOverlayLayer::PerformanceOverlayLayer(uint64_t options,
-                                                 const char* font_path)
-    : options_(options) {
-  if (font_path != nullptr) {
-    font_path_ = font_path;
-  }
-}
+PerformanceOverlayLayer::PerformanceOverlayLayer(uint64_t options)
+    : options_(options) {}
 
 void PerformanceOverlayLayer::Paint(PaintContext& context) const {
   const int padding = 8;
@@ -84,15 +73,15 @@ void PerformanceOverlayLayer::Paint(PaintContext& context) const {
   SkScalar height = paint_bounds().height() / 2;
   SkAutoCanvasRestore save(context.leaf_nodes_canvas, true);
 
-  VisualizeStopWatch(
-      *context.leaf_nodes_canvas, context.frame_time, x, y, width,
-      height - padding, options_ & kVisualizeRasterizerStatistics,
-      options_ & kDisplayRasterizerStatistics, "GPU", font_path_);
+  VisualizeStopWatch(*context.leaf_nodes_canvas, context.frame_time, x, y,
+                     width, height - padding,
+                     options_ & kVisualizeRasterizerStatistics,
+                     options_ & kDisplayRasterizerStatistics, "GPU");
 
   VisualizeStopWatch(*context.leaf_nodes_canvas, context.engine_time, x,
                      y + height, width, height - padding,
                      options_ & kVisualizeEngineStatistics,
-                     options_ & kDisplayEngineStatistics, "UI", font_path_);
+                     options_ & kDisplayEngineStatistics, "UI");
 }
 
 }  // namespace flow

flow/layers/performance_overlay_layer.h

@@ -5,8 +5,6 @@
 #ifndef FLUTTER_FLOW_LAYERS_PERFORMANCE_OVERLAY_LAYER_H_
 #define FLUTTER_FLOW_LAYERS_PERFORMANCE_OVERLAY_LAYER_H_
 
-#include <string>
-
 #include "flutter/flow/layers/layer.h"
 #include "flutter/fml/macros.h"
 
@@ -19,14 +17,12 @@ const int kVisualizeEngineStatistics = 1 << 3;
 
 class PerformanceOverlayLayer : public Layer {
  public:
-  explicit PerformanceOverlayLayer(uint64_t options,
-                                   const char* font_path = nullptr);
+  explicit PerformanceOverlayLayer(uint64_t options);
 
   void Paint(PaintContext& context) const override;
 
  private:
   int options_;
-  std::string font_path_;
 
   FML_DISALLOW_COPY_AND_ASSIGN(PerformanceOverlayLayer);
 };