Add support for computing iOS code coverage

Also disable failing PosixSignalDeliveryTest* tests for iOS

Bug: chromium:844647
Change-Id: I64bb233bef2f06f6778f2d475b6d3ad685fb9143
Reviewed-on: https://webrtc-review.googlesource.com/c/105641
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Peter Hanspers <peterhanspers@webrtc.org>
Reviewed-by: Artem Titarenko <artit@webrtc.org>
Commit-Queue: Artem Titarenko <artit@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25524}

test/ios/coverage_util_ios.mm

@@ -0,0 +1,42 @@
+/*
+ *  Copyright 2018 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import <Foundation/Foundation.h>
+
+#ifdef WEBRTC_IOS_ENABLE_COVERAGE
+extern "C" void __llvm_profile_set_filename(const char* name);
+#endif
+
+namespace rtc {
+namespace test {
+
+void ConfigureCoverageReportPath() {
+#ifdef WEBRTC_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  // ifdef WEBRTC_IOS_ENABLE_COVERAGE
+}
+
+}  // namespace test
+}  // namespace rtc