Remove Common.getAccountId and use Guice injection only

The server side code can use the Provider<CurrentUser> to obtain
the current user identity when it needs one.  The client side
only needs it in one place, Link, to compute the identity for
the "#mine" display.  This is easily obtained from the already
existing static account reference.  We might want to look at
using gwt-guice for the client side in the future, but that is
out of scope for now.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/server/workflow/NoOpFunction.java

@@ -15,7 +15,7 @@
 package com.google.gerrit.server.workflow;
 
 import com.google.gerrit.client.data.ApprovalType;
-import com.google.gerrit.client.reviewdb.Account;
+import com.google.gerrit.server.CurrentUser;
 
 /** A function that does nothing. */
 public class NoOpFunction extends CategoryFunction {
@@ -26,7 +26,7 @@ public class NoOpFunction extends CategoryFunction {
   }
 
   @Override
-  public boolean isValid(final Account.Id accountId, final ApprovalType at,
+  public boolean isValid(final CurrentUser user, final ApprovalType at,
       final FunctionState state) {
     return false;
   }