Fix parsing of intervals. defined in ms (#5151)

* Fix parsing of intervals. defined in ms

Fix parsing of intervals. defined in ms.
Increase accuracy for sub-second inrevals.
Closes #5008

* Tests for sub-ms intervals

Unit test for https://github.com/grafana/grafana/commit/2034d4b9710b0cb9fd0cdf14aa9981cd0417eda4

public/app/core/utils/kbn.js

@@ -12,9 +12,21 @@ function($, _) {
 
   kbn.round_interval = function(interval) {
     switch (true) {
-    // 0.3s
-    case (interval <= 300):
-      return 100;       // 0.1s
+    // 0.015s
+    case (interval <= 15):
+      return 10;      // 0.01s
+    // 0.035s
+    case (interval <= 35):
+      return 20;      // 0.02s
+    // 0.075s
+    case (interval <= 75):
+      return 50;       // 0.05s
+    // 0.15s
+    case (interval <= 150):
+      return 100;      // 0.1s
+    // 0.35s
+    case (interval <= 350):
+      return 200;      // 0.2s
     // 0.75s
     case (interval <= 750):
       return 500;       // 0.5s
@@ -133,7 +145,7 @@ function($, _) {
     return str;
   };
 
-  kbn.interval_regex = /(\d+(?:\.\d+)?)([Mwdhmsy])/;
+  kbn.interval_regex = /(\d+(?:\.\d+)?)(ms|[Mwdhmsy])/;
 
   // histogram & trends
   kbn.intervals_in_seconds = {
@@ -143,7 +155,8 @@ function($, _) {
     d: 86400,
     h: 3600,
     m: 60,
-    s: 1
+    s: 1,
+    ms: 0.001
   };
 
   kbn.calculateInterval = function(range, resolution, userInterval) {

public/test/core/utils/kbn_specs.js

@@ -147,5 +147,11 @@ define([
       var str = kbn.calculateInterval(range, 1000, '>10s');
       expect(str).to.be('20m');
     });
+	
+    it('10s 900 resolution and user low limit in ms', function() {
+      var range = { from: dateMath.parse('now-10s'), to: dateMath.parse('now') };
+      var str = kbn.calculateInterval(range, 900, '>15ms');
+      expect(str).to.be('15ms');
+    });
   });
 });