After r10021 we lost the ability to set the opacity of a Google layer. This makes layer.setOpacity work again by setting the opactiy of the shared GMap container. r=bartvde (pullup #2562)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10174 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Google.js

@@ -263,7 +263,10 @@ OpenLayers.Layer.Google = OpenLayers.Class(
      */
     setVisibility: function(visible) {
         this.setGMapVisibility(visible);
+        // sharing a map container, opacity has to be set per layer
+        var opacity = this.opacity == null ? 1 : this.opacity;
         OpenLayers.Layer.EventPane.prototype.setVisibility.apply(this, arguments);
+        this.setOpacity(opacity);
     },
     
     /**
@@ -303,6 +306,33 @@ OpenLayers.Layer.Google = OpenLayers.Class(
         }
     },
     
+    /**
+     * APIMethod: setOpacity
+     * Sets the opacity for the entire layer (all images)
+     * 
+     * Parameter:
+     * opacity - {Float}
+     */
+    setOpacity: function(opacity) {
+        if (opacity !== this.opacity) {
+            if (this.map != null) {
+                this.map.events.triggerEvent("changelayer", {
+                    layer: this,
+                    property: "opacity"
+                });
+            }
+            this.opacity = opacity;
+        }
+        // Though this layer's opacity may not change, we're sharing a container
+        // and need to update the opacity for the entire container.
+        if (this.getVisibility()) {
+            var container = this.mapObject.getContainer();
+            OpenLayers.Util.modifyDOMElement(
+                container, null, null, null, null, null, null, opacity
+            );
+        }
+    },
+
     /**
      * APIMethod: destroy
      * Clean up this layer.