Move logic of recording main thread scrolling reasons from cc to blink::ScrollManager

cc/input/main_thread_scrolling_reason.h

 // Copyright 2016 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.
 
 #ifndef CC_INPUT_MAIN_THREAD_SCROLLING_REASON_H_
 #define CC_INPUT_MAIN_THREAD_SCROLLING_REASON_H_
 
 #include <string>
 
 #include "base/stl_util.h"
@@ skipping 130 matching lines @@
     if (reasons & MainThreadScrollingReason::kNotScrollable)
       tracedValue->AppendString("Not scrollable");
     if (reasons & MainThreadScrollingReason::kContinuingMainThreadScroll)
       tracedValue->AppendString("Continuing main thread scroll");
     if (reasons & MainThreadScrollingReason::kNonInvertibleTransform)
       tracedValue->AppendString("Non-invertible transform");
     if (reasons & MainThreadScrollingReason::kPageBasedScrolling)
       tracedValue->AppendString("Page-based scrolling");
     tracedValue->EndArray();
   }
-
-  // For a given reason, return its index in enum
-  static int getReasonIndex(uint32_t reason) {
-    // Multiple reasons provided
-    if (reason & (reason - 1))
-      return -1;
-
-    int index = -1;
-    while (reason > 0) {
-      reason = reason >> 1;
-      ++index;
-    }
-    return index;
-  }
 };
 
 }  // namespace cc
 
 #endif  // CC_INPUT_MAIN_THREAD_SCROLLING_REASON_H_