Add tools for code coverage support in iOS.

testing/coverage_util_ios.mm

+// Copyright 2014 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.
+
+#import <Foundation/Foundation.h>
+
+extern "C" void __llvm_profile_set_filename(const char* name);
+
+namespace coverage_util {
+
+void SetupIfNecessary() {
+#if !defined(NDEBUG)// && defined(ENABLE_TEST_CODE_COVERAGE)

[lpromero, 2017/03/31 11:22:06]

I commented the ENABLE_TEST_CODE_COVERAGE variable. Should I replace it with
something more GN friendly?

+  static dispatch_once_t onceToken;

[Eugene But (OOO till 7-30), 2017/03/31 18:27:51]

s/onceToken/once_token

Same Style comment for the rest of variables

[lpromero, 2017/03/31 20:35:20]

Since this is now a .mm file, isn't it Objective-C style that applies? Or
because we are in a free function, we use C++ style? I change the style anyway,
just curious.

[Eugene But (OOO till 7-30), 2017/03/31 20:42:13]

C++ Style is used inside C-functions in C++ namespaces:
https://cs.chromium.org/chromium/src/styleguide/objective-c/objective-c.md?q=...

+  dispatch_once(&onceToken, ^{
+    // Writes the profraw file to the Documents directory, where the app has
+    // write rights.
+    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
+                                                         NSUserDomainMask, YES);
+    NSString *documentsDirectory = [paths firstObject];
+    NSString *fileName =
+        [documentsDirectory stringByAppendingPathComponent:@"coverage.profraw"];
+
+    // For documentation, see:
+    // http://clang.llvm.org/docs/SourceBasedCodeCoverage.html
+    __llvm_profile_set_filename([fileName UTF8String]);

[Eugene But (OOO till 7-30), 2017/03/31 18:27:51]

Use sys_string_conversions ?

[lpromero, 2017/03/31 20:35:20]

So there is a catch22 :)
base depends on //testing, so //testing can't depend on //base.

There is even a presubmit check that made the same comment as you!

+
+    // Print the path for easier retrieval.
+    NSLog(@"Coverage data at %@.", fileName);

[Eugene But (OOO till 7-30), 2017/03/31 18:27:51]

Should this be DLOG instead?

[lpromero, 2017/03/31 20:35:20]

Idem, I can't use base/logging.h.

+  });
+#endif
+}
+
+}  // namespace coverage_util