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>
+
+#import "testing/gtest/ios_enable_coverage.h"
+
+#if !defined(NDEBUG) && BUILDFLAG(IOS_ENABLE_COVERAGE)
+extern "C" void __llvm_profile_set_filename(const char* name);
+#endif
+
+namespace coverage_util {
+
+void SetupIfNecessary() {

[lpromero, 2017/04/27 15:34:28]

Maybe name this "ConfigureOutputPathIfCoverageEnabled".

[lpromero, 2017/04/27 15:44:26]

Seems like this describes more the implementation than the goal. Let say
tomorrow I want to add another condition, I will have to rename the method.

[sdefresne, 2017/04/28 08:06:25]

I agree. I think "ConfigureCoverageReportPath" is good. It does not depends on
the implementation (whether coverage is enabled, ...) while making it clear what
this function does (configure the path where the coverage report will be saved).

[lpromero, 2017/04/28 08:46:14]

Done. Thanks!

+#if !defined(NDEBUG) && BUILDFLAG(IOS_ENABLE_COVERAGE)
+  static dispatch_once_t once_token;
+  dispatch_once(&once_token, ^{
+    // Writes the profraw file to the Documents directory, where the app has
+    // write rights.
+    NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
+                                                         NSUserDomainMask, YES);
+    NSString* documents_directory = [paths firstObject];
+    NSString* file_name = [documents_directory
+        stringByAppendingPathComponent:@"coverage.profraw"];
+
+    // For documentation, see:
+    // http://clang.llvm.org/docs/SourceBasedCodeCoverage.html
+    __llvm_profile_set_filename(
+        [file_name cStringUsingEncoding:NSUTF8StringEncoding]);
+
+    // Print the path for easier retrieval.
+    NSLog(@"Coverage data at %@.", file_name);
+  });
+#endif
+}
+
+}  // namespace coverage_util