Add deprecation message for -webkit-background-composite

third_party/WebKit/Source/core/frame/UseCounter.cpp

Index: third_party/WebKit/Source/core/frame/UseCounter.cpp
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.cpp b/third_party/WebKit/Source/core/frame/UseCounter.cpp
index fb5b10670ed70e5eba1e36336e580c56851bf0de..3d0359d6fc3bbf9aff70dc2163b2be995e8fa0e6 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.cpp
+++ b/third_party/WebKit/Source/core/frame/UseCounter.cpp
@@ -730,11 +730,14 @@ void UseCounter::countDeprecationIfNotPrivateScript(v8::Isolate* isolate, Execut
     UseCounter::countDeprecation(context, feature);
 }
 
+// TODO (nainar): Migrate all console message functions to Deprecation
 static const char* milestoneString(int milestone)
 {
     switch (milestone) {
     case 50:
         return "M50, around April 2016";
+    case 51:
+        return "M51, around June 2016";
     case 53:
         return "M53, around September 2016";
     }
@@ -748,7 +751,7 @@ static String replacedBy(const char* feature, const char* replacement)
     return String::format("%s is deprecated. Please use %s instead.", feature, replacement);
 }
 
-static String willBeRemoved(const char* feature, int milestone, const char* details)
+String UseCounter::willBeRemoved(const char* feature, int milestone, const char* details)
 {
     return String::format("%s is deprecated and will be removed in %s. See https://www.chromestatus.com/features/%s for more details.", feature, milestoneString(milestone), details);
 }