Add an @Inject constructor to DefaultFilterPipeline so services which depend upon it can be used with Modules.requireAtInjectOnConstructorsModule()

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Manually synced.
COMMIT=33399588
diff --git a/extensions/servlet/src/com/google/inject/servlet/DefaultFilterPipeline.java b/extensions/servlet/src/com/google/inject/servlet/DefaultFilterPipeline.java
index 825d863..db32948 100755
--- a/extensions/servlet/src/com/google/inject/servlet/DefaultFilterPipeline.java
+++ b/extensions/servlet/src/com/google/inject/servlet/DefaultFilterPipeline.java
@@ -17,6 +17,7 @@
 
 import java.io.IOException;
 
+import javax.inject.Inject;
 import javax.servlet.FilterChain;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
@@ -30,6 +31,9 @@
  * @see com.google.inject.servlet.ManagedFilterPipeline See Also ManagedFilterPipeline.
  */
 class DefaultFilterPipeline implements FilterPipeline {
+  @Inject DefaultFilterPipeline() {
+  }
+
   public void initPipeline(ServletContext context) {
   }