[base/files] Respect MAC_CHROMIUM_TMPDIR instead of TMPDIR on macOS.

chrome/browser/extensions/api/developer_private/developer_private_api_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/developer_private/developer_private_api.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/files/file_util.h"
@@ skipping 586 matching lines @@
 
   // Load an extension with a clear manifest error ('version' is invalid).
   TestExtensionDir dir;
   dir.WriteManifest(
       R"({
            "name": "foo",
            "description": "bar",
            "version": 1,
            "manifest_version": 2
          })");
-  base::FilePath path = dir.UnpackedPath();
+  base::FilePath path = base::MakeAbsoluteFilePath(dir.UnpackedPath());

[Devlin, 2017/03/29 15:15:43]

Hmm... this doesn't seem like quite the right place to do this.  A few different
options:
- At minimum, we should probably hoist this up to TestExtensionDir::UnpackedPath
(and probably apply a similar change to the value returned by Pack()).  I
*think* that will be a fairly easy change that doesn't break anything.
- That said, TestExtensionDir basically just relies on ScopedTempDir - would it
make sense to have ScopedTempDir return the absolute path to prevent this kind
of misuse?  I don't know if anything is currently relying on a non-absolute path
being returned by ScopedTempDir...
- How crazy would it be for FilePath::operator== to return true if the absolute
paths are the same?

I'd probably be fine with any of these options, but if we go for the less
general-case one (modifying TestExtensionDir), it'd be good to know the
reasoning for why the others would be incorrect.

   api::EntryPicker::SkipPickerAndAlwaysSelectPathForTest(&path);
 
   DeveloperPrivateAPI::UnpackedRetryId retry_guid;
   {
     // Trying to load the extension should result in a load error with the
     // retry id populated.
     scoped_refptr<UIThreadExtensionFunction> function(
         new api::DeveloperPrivateLoadUnpackedFunction());
     function->SetRenderFrameHost(web_contents->GetMainFrame());
     std::unique_ptr<base::Value> result =
@@ skipping 263 matching lines @@
   EXPECT_TRUE(
       profile()->GetPrefs()->GetBoolean(prefs::kExtensionsUIDeveloperMode));
 
   std::unique_ptr<api::developer_private::ProfileInfo> profile_info;
   ASSERT_NO_FATAL_FAILURE(GetProfileConfiguration(&profile_info));
   EXPECT_TRUE(profile_info->in_developer_mode);
   EXPECT_FALSE(profile_info->is_developer_mode_controlled_by_policy);
 }
 
 }  // namespace extensions