Ignore stderr failure messages on iossim when not running xctests.

testing/iossim/iossim.mm

 // Copyright (c) 2012 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>
 #if defined(__MAC_10_12) && __MAC_OS_X_VERSION_MAX_ALLOWED >= __MAC_10_12
 #include <getopt.h>
 #include <string>
 
 namespace {
 
@@ skipping 240 matching lines @@
   NSData* data = [NSPropertyListSerialization
       dataFromPropertyList:xctestrun
                     format:NSPropertyListXMLFormat_v1_0
           errorDescription:&error];
   [data writeToFile:tempFilePath atomically:YES];
   XCRunTask* task = [[[XCRunTask alloc] initWithArguments:@[
     @"xcodebuild", @"-xctestrun", tempFilePath, @"-destination",
     [@"platform=iOS Simulator,id=" stringByAppendingString:udid],
     @"test-without-building"
   ]] autorelease];
+
+  // The following stderr messages are meaningless on iossim when not running
+  // xctests and can be safely stripped.
+  if (!xctest_path) {
+    NSPipe* stderr_pipe = [NSPipe pipe];
+    stderr_pipe.fileHandleForReading.readabilityHandler =
+        ^(NSFileHandle* handle) {
+          NSString* log = [[[NSString alloc] initWithData:handle.availableData
+                                                 encoding:NSUTF8StringEncoding]
+              autorelease];
+          if ([log containsString:@"IDETestOperationsObserverErrorDomain"] ||
+              [log containsString:@"** TEST EXECUTE FAILED **"]) {
+            return;
+          }
+          printf("%s", [log UTF8String]);
+        };
+    [task setStandardError:stderr_pipe];
+  }
   [task run];
 }
 
 int main(int argc, char* const argv[]) {
   NSString* app_path = nil;
   NSString* xctest_path = nil;
   NSString* cmd_args = nil;
   NSString* device_name = @"iPhone 6s";
   bool wants_wipe = false;
   bool wants_print_home = false;
@@ skipping 965 matching lines @@
   }
 
   // Note that this code is only executed if the simulator fails to start
   // because once the main run loop is started, only the delegate calling
   // exit() will end the program.
   [pool drain];
   return kExitFailure;
 }
 
 #endif