blink: Make WebMainThreadScrollingReason wrap the cc enum.

This moves the WebMainThreadScrollingReason from public/platform/ to
platform/scroll/, as it is no longer used in the WebLayer API
explicitly, and renames it to just MainThreadScrollingReason. We change
the type to be an alias for the cc type instead of maintaining static
asserts that they match.

Depends on: https://codereview.chromium.org/1604053002/
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1602773006

Cr-Commit-Position: refs/heads/master@{#371151}

2 files changed, 6 insertions, 44 deletions

diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index 992157b..41efb47 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -343,51 +343,15 @@ bool WebLayerImpl::haveScrollEventHandlers() const {
   return layer_->have_scroll_event_handlers();
 }
 
-static_assert(static_cast<uint32_t>(
-                  blink::WebMainThreadScrollingReason::NotScrollingOnMain) ==
-                  cc::MainThreadScrollingReason::kNotScrollingOnMain,
-              "MainThreadScrollingReason and "
-              "WebMainThreadScrollingReason enums must match");
-static_assert(
-    static_cast<uint32_t>(blink::WebMainThreadScrollingReason::
-                              HasBackgroundAttachmentFixedObjects) ==
-        cc::MainThreadScrollingReason::kHasBackgroundAttachmentFixedObjects,
-    "MainThreadScrollingReason and "
-    "WebMainThreadScrollingReason enums must match");
-static_assert(
-    static_cast<uint32_t>(blink::WebMainThreadScrollingReason::
-                              HasNonLayerViewportConstrainedObjects) ==
-        cc::MainThreadScrollingReason::kHasNonLayerViewportConstrainedObjects,
-    "MainThreadScrollingReason and "
-    "WebMainThreadScrollingReason enums must match");
-static_assert(
-    static_cast<uint32_t>(
-        blink::WebMainThreadScrollingReason::ThreadedScrollingDisabled) ==
-        cc::MainThreadScrollingReason::kThreadedScrollingDisabled,
-    "MainThreadScrollingReason and "
-    "WebMainThreadScrollingReason enums must match");
-static_assert(static_cast<uint32_t>(
-                  blink::WebMainThreadScrollingReason::ScrollBarScrolling) ==
-                  cc::MainThreadScrollingReason::kScrollbarScrolling,
-              "MainThreadScrollingReason and "
-              "WebMainThreadScrollingReason enums must match");
-static_assert(
-    static_cast<uint32_t>(blink::WebMainThreadScrollingReason::PageOverlay) ==
-        cc::MainThreadScrollingReason::kPageOverlay,
-    "MainThreadScrollingReason and "
-    "WebMainThreadScrollingReason enums must match");
-
 void WebLayerImpl::addMainThreadScrollingReasons(
-    blink::WebMainThreadScrollingReason::WebMainThreadScrollingReason
-        main_thread_scrolling_reasons) {
+    uint32_t main_thread_scrolling_reasons) {
   DCHECK(main_thread_scrolling_reasons);
   // WebLayerImpl should only know about non-transient scrolling
   // reasons. Transient scrolling reasons are computed per hit test.
-  DCHECK_LE(
-      main_thread_scrolling_reasons,
-      static_cast<
-          blink::WebMainThreadScrollingReason::WebMainThreadScrollingReason>(
-          cc::MainThreadScrollingReason::kMaxNonTransientScrollingReason));
+  // TODO(tdresser): This is comparing less than a bit flag but that's not valid
+  // if there is more than one reason given in |main_thread_scrolling_reasons|.
+  DCHECK_LE(main_thread_scrolling_reasons,
+            cc::MainThreadScrollingReason::kMaxNonTransientScrollingReason);
   layer_->AddMainThreadScrollingReasons(main_thread_scrolling_reasons);
 }
 
diff --git a/cc/blink/web_layer_impl.h b/cc/blink/web_layer_impl.h
index 482c633..f63ba55 100644
--- a/cc/blink/web_layer_impl.h
+++ b/cc/blink/web_layer_impl.h
@@ -22,7 +22,6 @@
 #include "third_party/WebKit/public/platform/WebDoublePoint.h"
 #include "third_party/WebKit/public/platform/WebFloatPoint.h"
 #include "third_party/WebKit/public/platform/WebLayer.h"
-#include "third_party/WebKit/public/platform/WebMainThreadScrollingReason.h"
 #include "third_party/WebKit/public/platform/WebPoint.h"
 #include "third_party/WebKit/public/platform/WebRect.h"
 #include "third_party/WebKit/public/platform/WebSize.h"
@@ -130,8 +129,7 @@ class WebLayerImpl : public blink::WebLayer {
   void setHaveScrollEventHandlers(bool have_scroll_event_handlers) override;
   bool haveScrollEventHandlers() const override;
   void addMainThreadScrollingReasons(
-      blink::WebMainThreadScrollingReason::WebMainThreadScrollingReason
-          main_thread_scrolling_reasons) override;
+      uint32_t main_thread_scrolling_reasons) override;
   void clearMainThreadScrollingReasons() override;
   bool shouldScrollOnMainThread() const override;
   void setNonFastScrollableRegion(