Turn on many more Eclipse warnings, and fix them

- Warn on empty statements, e.g. "for (;;);". These may be
   typos and are easily replaced by "for (;;) {}" which is more
   explicit.
 - Warn on field hiding. This allows cleanup of many acceptance test
   members, at the cost of a couple of renames and the occasional
   suppression (when the field is in a public nested enum that shadows
   a public constant).
 - Warn on unnecessary casts.
 - Warn on unused declared thrown exceptions. In addition to reducing
   method signature length and number of imports, this also eliminated
   some impossible catch blocks.
 - Warn on missing @Override annotations.
 - Warn on unused parameters. This is likely the most controversial,
   as a few relatively common patterns require unused parameters in a
   way that Eclipse can't ignore. However, it also resulted in cleanup
   of a lot of unnecessary injections and method parameters, so I
   think the cost was worth it.

Change-Id: I7224be8b1c798613a127c88507e8cce400679e5d

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/clippy/client/CopyableLabel.java

@@ -160,10 +160,12 @@ public class CopyableLabel extends Composite implements HasText {
     }
   }
 
+  @Override
   public String getText() {
     return text;
   }
 
+  @Override
   public void setText(final String newText) {
     text = newText;
     visibleLen = newText.length();
@@ -195,6 +197,7 @@ public class CopyableLabel extends Composite implements HasText {
                   @Override
                   public void onKeyUp(final KeyUpEvent event) {
                     Scheduler.get().scheduleDeferred(new Command() {
+                      @Override
                       public void execute() {
                         hideTextBox();
                       }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/AttMap.java

@@ -107,11 +107,13 @@ class AttMap {
   }
 
   private static class AnyTag implements Tag {
+    @Override
     public void assertSafe(String name, String value) {
     }
   }
 
   private static class AnchorTag implements Tag {
+    @Override
     public void assertSafe(String name, String value) {
       if ("href".equals(name)) {
         assertNotJavascriptUrl(value);
@@ -120,6 +122,7 @@ class AttMap {
   }
 
   private static class FormTag implements Tag {
+    @Override
     public void assertSafe(String name, String value) {
       if ("action".equals(name)) {
         assertNotJavascriptUrl(value);
@@ -128,6 +131,7 @@ class AttMap {
   }
 
   private static class SrcTag implements Tag {
+    @Override
     public void assertSafe(String name, String value) {
       if ("src".equals(name)) {
         assertNotJavascriptUrl(value);

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/Buffer.java

@@ -29,5 +29,6 @@ interface Buffer {
 
   void append(String v);
 
+  @Override
   String toString();
 }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/BufferDirect.java

@@ -21,30 +21,37 @@ final class BufferDirect implements Buffer {
     return strbuf.length() == 0;
   }
 
+  @Override
   public void append(final boolean v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final char v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final int v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final long v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final float v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final double v) {
     strbuf.append(v);
   }
 
+  @Override
   public void append(final String v) {
     strbuf.append(v);
   }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/BufferSealElement.java

@@ -21,30 +21,37 @@ final class BufferSealElement implements Buffer {
     shb = safeHtmlBuilder;
   }
 
+  @Override
   public void append(final boolean v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final char v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final double v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final float v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final int v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final long v) {
     shb.sealElement().append(v);
   }
 
+  @Override
   public void append(final String v) {
     shb.sealElement().append(v);
   }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/HighlightSuggestOracle.java

@@ -41,6 +41,7 @@ public abstract class HighlightSuggestOracle extends SuggestOracle {
   @Override
   public final void requestSuggestions(final Request request, final Callback cb) {
     onRequestSuggestions(request, new Callback() {
+      @Override
       public void onSuggestionsReady(final Request request,
           final Response response) {
         final String qpat = getQueryPattern(request.getQuery());
@@ -99,10 +100,12 @@ public abstract class HighlightSuggestOracle extends SuggestOracle {
     private static native String sgi(String inString, String pat, String newHtml)
     /*-{ return inString.replace(RegExp(pat, 'gi'), newHtml); }-*/;
 
+    @Override
     public String getDisplayString() {
       return displayString;
     }
 
+    @Override
     public String getReplacementString() {
       return suggestion.getReplacementString();
     }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java

@@ -44,26 +44,32 @@ public abstract class SafeHtml
         @Override
         public SafeHtmlCss css() {
           return new SafeHtmlCss() {
+            @Override
             public String wikiList() {
               return "wikiList";
             }
 
+            @Override
             public String wikiPreFormat() {
               return "wikiPreFormat";
             }
 
+            @Override
             public String wikiQuote() {
               return "wikiQuote";
             }
 
+            @Override
             public boolean ensureInjected() {
               return false;
             }
 
+            @Override
             public String getName() {
               return null;
             }
 
+            @Override
             public String getText() {
               return null;
             }
@@ -335,5 +341,6 @@ public abstract class SafeHtml
   }
 
   /** @return a clean HTML string safe for inclusion in any context. */
+  @Override
   public abstract String asString();
 }

gerrit-gwtexpui/src/main/java/com/google/gwtexpui/server/CacheControlFilter.java

@@ -49,12 +49,15 @@ import javax.servlet.http.HttpServletResponse;
  * </pre>
  */
 public class CacheControlFilter implements Filter {
+  @Override
   public void init(final FilterConfig config) {
   }
 
+  @Override
   public void destroy() {
   }
 
+  @Override
   public void doFilter(final ServletRequest sreq, final ServletResponse srsp,
       final FilterChain chain) throws IOException, ServletException {
     final HttpServletRequest req = (HttpServletRequest) sreq;