Make dropdowns update correctly when you switch between images. (#1321)

core/field.js

@@ -462,6 +462,17 @@ Blockly.Field.prototype.setText = function(newText) {
     return;
   }
   this.text_ = newText;
+  this.forceRerender();
+};
+
+/**
+ * Force a rerender of the block that this field is installed on, which will
+ * rerender this field and adjust for any sizing changes.
+ * Other fields on the same block will not rerender, because their sizes have
+ * already been recorded.
+ * @package
+ */
+Blockly.Field.prototype.forceRerender = function() {
   // Set width to 0 to force a rerender of this field.
   this.size_.width = 0;
 

core/field_dropdown.js

@@ -413,17 +413,20 @@ Blockly.FieldDropdown.prototype.setValue = function(newValue) {
       var content = options[i][0];
       if (typeof content == 'object') {
         this.imageJson_ = content;
-        this.setText(content.alt);
+        this.text_ = content.alt;
       } else {
         this.imageJson_ = null;
-        this.setText(content);
+        this.text_ = content;
       }
+      // Always rerender if either the value or the text has changed.
+      this.forceRerender();
       return;
     }
   }
   // Value not found.  Add it, maybe it will become valid once set
   // (like variable names).
-  this.setText(newValue);
+  this.text_ = newValue;
+  this.forceRerender();
 };
 
 /**