Hide SafeHtml.asString from client code

Converting a SafeHtml into a String may lead to unsafe patterns
such as calling setInnerHTML directly, possibly after doing an
unsafe string concatenation.  By hiding the method we reduce
the ability for client code to make this innocent mistake.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java
index 311584a..eef4a96 100644
--- a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java
+++ b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtml.java
@@ -115,5 +115,5 @@
   }
 
   /** @return a clean HTML string safe for inclusion in any context. */
-  public abstract String asString();
+  abstract String asString();
 }
diff --git a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilder.java b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilder.java
index a46a47e..238a102 100644
--- a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilder.java
+++ b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlBuilder.java
@@ -361,7 +361,7 @@
   }
 
   @Override
-  public String asString() {
+  String asString() {
     return cb.toString();
   }
 
diff --git a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlString.java b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlString.java
index 781e494..4d500fe 100644
--- a/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlString.java
+++ b/src/main/java/com/google/gwtexpui/safehtml/client/SafeHtmlString.java
@@ -22,7 +22,7 @@
   }
 
   @Override
-  public String asString() {
+  String asString() {
     return html;
   }
 }