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

runtime/platform/hashmap.h

 // 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.
 
 #ifndef RUNTIME_PLATFORM_HASHMAP_H_
 #define RUNTIME_PLATFORM_HASHMAP_H_
 
 #include "platform/globals.h"
 
 namespace dart {
 
 class HashMap {
  public:
-  typedef bool (*MatchFun) (void* key1, void* key2);
+  typedef bool (*MatchFun)(void* key1, void* key2);
 
-  typedef void (*ClearFun) (void* value);
+  typedef void (*ClearFun)(void* value);
 
   // initial_capacity is the size of the initial hash map;
   // it must be a power of 2 (and thus must not be 0).
   HashMap(MatchFun match, uint32_t initial_capacity);
 
   ~HashMap();
 
-  static bool SamePointerValue(void* key1, void* key2) {
-    return key1 == key2;
-  }
+  static bool SamePointerValue(void* key1, void* key2) { return key1 == key2; }
 
   static uint32_t StringHash(char* key) {
     uint32_t hash_ = 0;
     if (key == NULL) return hash_;
     int len = strlen(key);
     for (int i = 0; i < len; i++) {
       hash_ += key[i];
       hash_ += hash_ << 10;
       hash_ ^= hash_ >> 6;
     }
@@ skipping 62 matching lines @@
   void Initialize(uint32_t capacity);
   void Resize();
 
   friend class IntSet;  // From hashmap_test.cc
   DISALLOW_COPY_AND_ASSIGN(HashMap);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_PLATFORM_HASHMAP_H_