Tweak test

Author: ColdPaleLight

impeller/display_list/display_list_unittests.cc

@@ -290,7 +290,7 @@ TEST_P(DisplayListTest, SaveLayerWithFiltersAndAlphaDrawCorrectly) {
       ImGui::SetNextWindowPos({10, 10});
     }
 
-    static float alpha = 0.8;
+    static float alpha = 0.5;
     static int selected_type = 0;
     const char* names[] = {"Use as image filter", "Use as color filter",
                            "Disable filter"};
@@ -299,7 +299,7 @@ TEST_P(DisplayListTest, SaveLayerWithFiltersAndAlphaDrawCorrectly) {
         1, 0, 0, 0, 0,  //
         0, 3, 0, 0, 0,  //
         0, 0, 1, 0, 0,  //
-        0, 0, 0, 0, 0,  //
+        0, 0, 0, 1, 0,  //
     };
 
     ImGui::Begin("Controls", nullptr, ImGuiWindowFlags_AlwaysAutoResize);