Fix pixel diff unit tests

For some trunk builders, they set env var CHROMIUM_TEST_LAUNCHER_BOT_MODE.
For unit test, we need to unset the var to test some scenario.
https://source.chromium.org/chromium/chromium/src/+/master:ui/base/test/skia_gold_pixel_diff.cc;l=153;drc=07e4c76dd0f6b37146a1c35e4a96fae53aff7371

Bug: 1146399
Change-Id: Ifb71831060a4bd779ef48e83ca8d66741e5e57e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2523555Reviewed-by: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Albert J. Wong <ajwong@chromium.org>
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825590}

base/test/scoped_environment_variable_override.cc

@@ -11,15 +11,28 @@ namespace test {
 
 ScopedEnvironmentVariableOverride::ScopedEnvironmentVariableOverride(
     const std::string& variable_name,
-    const std::string& value)
+    const std::string& value,
+    bool unset_var)
     : environment_(Environment::Create()),
       variable_name_(variable_name),
       overridden_(false),
       was_set_(false) {
   was_set_ = environment_->GetVar(variable_name, &old_value_);
-  overridden_ = environment_->SetVar(variable_name, value);
+  if (unset_var)
+    overridden_ = environment_->UnSetVar(variable_name);
+  else
+    overridden_ = environment_->SetVar(variable_name, value);
 }
 
+ScopedEnvironmentVariableOverride::ScopedEnvironmentVariableOverride(
+    const std::string& variable_name,
+    const std::string& value)
+    : ScopedEnvironmentVariableOverride(variable_name, value, false) {}
+
+ScopedEnvironmentVariableOverride::ScopedEnvironmentVariableOverride(
+    const std::string& variable_name)
+    : ScopedEnvironmentVariableOverride(variable_name, "", true) {}
+
 ScopedEnvironmentVariableOverride::~ScopedEnvironmentVariableOverride() {
   if (overridden_) {
     if (was_set_)

base/test/scoped_environment_variable_override.h

@@ -20,6 +20,8 @@ class ScopedEnvironmentVariableOverride final {
  public:
   ScopedEnvironmentVariableOverride(const std::string& variable_name,
                                     const std::string& value);
+  // Unset the variable.
+  explicit ScopedEnvironmentVariableOverride(const std::string& variable_name);
   ~ScopedEnvironmentVariableOverride();
 
   base::Environment* GetEnv() { return environment_.get(); }
@@ -27,6 +29,9 @@ class ScopedEnvironmentVariableOverride final {
   bool WasSet() { return was_set_; }
 
  private:
+  ScopedEnvironmentVariableOverride(const std::string& variable_name,
+                                    const std::string& value,
+                                    bool unset_var);
   std::unique_ptr<Environment> environment_;
   std::string variable_name_;
   bool overridden_;

ui/base/test/skia_gold_pixel_diff_unittest.cc

@@ -6,6 +6,7 @@
 
 #include "base/command_line.h"
 #include "base/files/file_util.h"
+#include "base/test/scoped_environment_variable_override.h"
 #include "base/test/test_switches.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -108,6 +109,8 @@ TEST_F(SkiaGoldPixelDiffTest, LocalNoLuciAuth) {
   MockSkiaGoldPixelDiff mock_pixel;
   auto* cmd_line = base::CommandLine::ForCurrentProcess();
   cmd_line->RemoveSwitch(switches::kTestLauncherBotMode);
+  base::test::ScopedEnvironmentVariableOverride env_override(
+      "CHROMIUM_TEST_LAUNCHER_BOT_MODE");
 
   EXPECT_CALL(mock_pixel, LaunchProcess(_)).Times(AnyNumber());
   EXPECT_CALL(mock_pixel, LaunchProcess(AllOf(Property(
@@ -349,6 +352,8 @@ TEST_F(SkiaGoldPixelDiffTest, MakeGerritCommentInvalidFlag) {
 TEST_F(SkiaGoldPixelDiffTest, DryRunLocally) {
   auto* cmd_line = base::CommandLine::ForCurrentProcess();
   cmd_line->RemoveSwitch(switches::kTestLauncherBotMode);
+  base::test::ScopedEnvironmentVariableOverride env_override(
+      "CHROMIUM_TEST_LAUNCHER_BOT_MODE");
 
   MockSkiaGoldPixelDiff mock_pixel;
   EXPECT_CALL(mock_pixel, LaunchProcess(_)).Times(AnyNumber());