Bug 1546697 - Use a consistent style for enum classes in layout. r=dholbert

Per the discussion in:

  https://groups.google.com/d/msg/mozilla.dev.platform/P79pwa9z5m8/iPYPAWPHCAAJ

They should be CamelCase, and that's what most of them already do. This converts
the rest, which are a few.

For the ones that already used `e` or `k` prefixes, I've mostly done:

 for file in $(rg Type::e layout | cut -d : -f 1 | sort | uniq); do sed -i 's#Type::e#Type::#g' $file; done

For the ones that used uppercase, I've removed the prefix if it was already in
the type name, and turn them into CamelCase.

Depends on D28680

Differential Revision: https://phabricator.services.mozilla.com/D28681

docshell/base/nsDocShell.cpp

@@ -5659,10 +5659,10 @@ nsresult nsDocShell::SetCurScrollPosEx(int32_t aCurHorizontalPos,
   nsIScrollableFrame* sf = GetRootScrollFrame();
   NS_ENSURE_TRUE(sf, NS_ERROR_FAILURE);
 
-  ScrollMode scrollMode = ScrollMode::eInstant;
+  ScrollMode scrollMode = ScrollMode::Instant;
   if (sf->GetScrollStyles().mScrollBehavior ==
       NS_STYLE_SCROLL_BEHAVIOR_SMOOTH) {
-    scrollMode = ScrollMode::eSmoothMsd;
+    scrollMode = ScrollMode::SmoothMsd;
   }
 
   nsPoint targetPos(aCurHorizontalPos, aCurVerticalPos);