Improve restrictions on UsageTimeLimit policy schema.

Change-Id: Iac4be6a4a32ca598f9e90a0033a651fc8a43eb62
Reviewed-on: https://chromium-review.googlesource.com/1160722Reviewed-by: Lutz Justen <ljusten@chromium.org>
Commit-Queue: Henrique Grandinetti <hgrandinetti@google.com>
Cr-Commit-Position: refs/heads/master@{#580515}

components/policy/resources/policy_templates.json

@@ -12121,8 +12121,16 @@
                       'type': 'object',
                       'id': 'Time',
                       'properties': {
-                        'hour': { 'type': 'integer' },
-                        'minute': { 'type': 'integer'}
+                        'hour': {
+                          'type': 'integer',
+                          'minimum': 0,
+                          'maximum': 23
+                        },
+                        'minute': {
+                          'type': 'integer',
+                          'minimum': 0,
+                          'maximum': 59
+                        },
                       }
                     },
                     'ends_at': { '$ref': 'Time' },
@@ -12139,7 +12147,10 @@
                 'type': 'object',
                 'id': 'TimeUsageLimitEntry',
                 'properties': {
-                  'usage_quota_mins': { 'type': 'integer' },
+                  'usage_quota_mins': {
+                    'type': 'integer',
+                    'minimum': 0
+                  },
                   'last_updated_millis': { 'type': 'string' }
                 }
               },
@@ -12168,7 +12179,10 @@
                 'action_specific_data': {
                   'type': 'object',
                   'properties': {
-                    'duration_mins': { 'type': 'integer' }
+                    'duration_mins': {
+                      'type': 'integer',
+                      'minimum': 0
+                    }
                   }
                 }
               }