Work arround for slower template variable dropdown when variable has many…

Work arround for slower template variable dropdown when variable has many thousand values, now only top 1000 values are rendered to html, you can still search all values, Closes #2246

public/app/directives/valueSelectDropdown.js

@@ -29,7 +29,11 @@ function (angular, app, _) {
           return tag;
         });
 
-        vm.search = {query: '', options: vm.options};
+        vm.search = {
+          query: '',
+          options: vm.options.slice(0, Math.min(vm.options.length, 1000))
+        };
+
         vm.dropdownVisible = true;
       };
 
@@ -204,6 +208,8 @@ function (angular, app, _) {
         vm.search.options = _.filter(vm.options, function(option) {
           return option.text.toLowerCase().indexOf(vm.search.query.toLowerCase()) !== -1;
         });
+
+        vm.search.options = vm.search.options.slice(0, Math.min(vm.search.options.length, 1000));
       };
 
       vm.init = function() {

public/app/features/templating/templateValuesSrv.js

@@ -10,6 +10,7 @@ function (angular, _, kbn) {
 
   module.service('templateValuesSrv', function($q, $rootScope, datasourceSrv, $location, templateSrv, timeSrv) {
     var self = this;
+
     function getNoneOption() { return { text: 'None', value: '', isNone: true }; }
 
     $rootScope.onAppEvent('time-range-changed', function()  {

public/app/partials/valueSelectDropdown.html

@@ -19,7 +19,7 @@
 					<span class="variable-option-icon"></span>
 					Selected ({{vm.selectedValues.length}})
 				</a>
-				<a class="variable-option pointer" bindonce ng-repeat="option in vm.search.options" ng-class="{'selected': option.selected, 'highlighted': $index === vm.highlightIndex}" ng-click="vm.selectValue(option, $event)">
+				<a class="variable-option pointer" ng-repeat="option in vm.search.options" ng-class="{'selected': option.selected, 'highlighted': $index === vm.highlightIndex}" ng-click="vm.selectValue(option, $event)">
 					<span class="variable-option-icon"></span>
 					<span>{{option.text}}</span>
 				</a>