Bug 742788: Fix two 'warning: comparison of unsigned expression >= 0 is always true' in js. r=luke

js/src/jsinterp.cpp

@@ -951,7 +951,6 @@ LeaveWith(JSContext *cx)
 {
     WithObject &withobj = cx->fp()->scopeChain().asWith();
     JS_ASSERT(withobj.maybeStackFrame() == js_FloatingFrameIfGenerator(cx, cx->fp()));
-    JS_ASSERT(withobj.stackDepth() >= 0);
     withobj.setStackFrame(NULL);
     cx->fp()->setScopeChainNoCallObj(withobj.enclosingScope());
 }

js/src/jsopcode.cpp

@@ -775,7 +775,7 @@ Sprinter::stringAt(ptrdiff_t off) const
 char &
 Sprinter::operator[](size_t off)
 {
-    JS_ASSERT(off >= 0 && (size_t) off < size);
+    JS_ASSERT(off < size);
     return *(base + off);
 }