Add .clang-format and run clang-format on runtime/platform.

runtime/platform/assert.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 
 #include "platform/globals.h"
 #include "vm/os.h"
 #include "vm/profiler.h"
 
@@ skipping 10 matching lines @@
   // Print the file and line number into the buffer.
   char buffer[4 * KB];
   MSAN_UNPOISON(buffer, sizeof(buffer));
   intptr_t file_and_line_length =
       snprintf(buffer, sizeof(buffer), "%s: %d: error: ", file, line_);
 
   // Print the error message into the buffer.
   va_list arguments;
   va_start(arguments, format);
   vsnprintf(buffer + file_and_line_length,
-            sizeof(buffer) - file_and_line_length,
-            format,
-            arguments);
+            sizeof(buffer) - file_and_line_length, format, arguments);
   va_end(arguments);
 
   // Print the buffer on stderr and/or syslog.
   OS::PrintErr("%s\n", buffer);
 
   // In case of failed assertions, abort right away. Otherwise, wait
   // until the program is exiting before producing a non-zero exit
   // code through abort.
   if (kind_ == ASSERT) {
     NOT_IN_PRODUCT(Profiler::DumpStackTrace(true /* native_stack_trace */));
     OS::Abort();
   }
   failed_ = true;
 }
 
 }  // namespace dart