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

runtime/platform/assert.cc

Index: runtime/platform/assert.cc
diff --git a/runtime/platform/assert.cc b/runtime/platform/assert.cc
index 524c7a2470fa4f75d007dfd12b3fe97024321a0f..49c6bec4c00d37c51a76f36e5b484bf2984610e7 100644
--- a/runtime/platform/assert.cc
+++ b/runtime/platform/assert.cc
@@ -28,9 +28,7 @@ void DynamicAssertionHelper::Fail(const char* format, ...) {
   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.