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

cc/input/main_thread_scrolling_reason.h

Index: cc/input/main_thread_scrolling_reason.h
diff --git a/cc/input/main_thread_scrolling_reason.h b/cc/input/main_thread_scrolling_reason.h
index a8c586eee95ab06c830406147aae2ebab941929d..9746d9425740d96ff63e52707b498f08b4878d80 100644
--- a/cc/input/main_thread_scrolling_reason.h
+++ b/cc/input/main_thread_scrolling_reason.h
@@ -37,14 +37,12 @@
     // These *AndLCDText reasons are due to subpixel text rendering which can
     // only be applied by blending glyphs with the background at a specific
     // screen position; transparency and transforms break this.
-    kNonCompositedReasonsFirst = 16,
     kHasOpacityAndLCDText = 1 << 16,
     kHasTransformAndLCDText = 1 << 17,
     kBackgroundNotOpaqueInRectAndLCDText = 1 << 18,
     kHasBorderRadius = 1 << 19,
     kHasClipRelatedProperty = 1 << 20,
     kHasBoxShadowFromNonRootLayer = 1 << 21,
-    kNonCompositedReasonsLast = 21,
 
     // Transient scrolling reasons. These are computed for each scroll begin.
     kNonFastScrollableRegion = 1 << 5,
@@ -62,11 +60,6 @@
     kMainThreadScrollingReasonCount = 22,
   };
 
-  static const uint32_t kNonCompositedReasons =
-      kHasOpacityAndLCDText | kHasTransformAndLCDText |
-      kBackgroundNotOpaqueInRectAndLCDText | kHasBorderRadius |
-      kHasClipRelatedProperty | kHasBoxShadowFromNonRootLayer;
-
   // Returns true if the given MainThreadScrollingReason can be set by the main
   // thread.
   static bool MainThreadCanSetScrollReasons(uint32_t reasons) {
@@ -74,7 +67,10 @@
         kNotScrollingOnMain | kHasBackgroundAttachmentFixedObjects |
         kHasNonLayerViewportConstrainedObjects | kThreadedScrollingDisabled |
         kScrollbarScrolling | kPageOverlay | kHandlingScrollFromMainThread |
-        kCustomScrollbarScrolling;
+        kCustomScrollbarScrolling | kHasOpacityAndLCDText |
+        kHasTransformAndLCDText | kBackgroundNotOpaqueInRectAndLCDText |
+        kHasBorderRadius | kHasClipRelatedProperty |
+        kHasBoxShadowFromNonRootLayer;
     return (reasons & reasons_set_by_main_thread) == reasons;
   }
 
@@ -86,12 +82,6 @@
         kNotScrollable | kContinuingMainThreadScroll | kNonInvertibleTransform |
         kPageBasedScrolling;
     return (reasons & reasons_set_by_compositor) == reasons;
-  }
-
-  // Returns true if there are any reasons that prevented the scroller
-  // from being composited.
-  static bool HasNonCompositedScrollReasons(uint32_t reasons) {
-    return (reasons & kNonCompositedReasons) != 0;
   }
 
   static std::string mainThreadScrollingReasonsAsText(uint32_t reasons) {
@@ -158,6 +148,20 @@
       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