I have created a sales dashboard in which I want to show a comparison of the current month's sales with last month's sale using Google Line Charts. 

I have added the following code in my dashboard for testing Google Charts:

  <script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
<script type="text/javascript">
google.charts.load('current', {packages: ['corechart', 'line']});
google.charts.setOnLoadCallback(drawLineColors);
function drawLineColors() {
      var data = new google.visualization.DataTable();
      data.addColumn('number', 'X');
      data.addColumn('number', 'Dogs');
      data.addColumn('number', 'Cats');
      data.addRows([
        [0, 0, 0],    [1, 10, 5],   [2, 23, 15],  [3, 17, 9],   [4, 18, 10],  [5, 9, 5],
        [6, 11, 3],   [7, 27, 19],  [8, 33, 25],  [9, 40, 32],  [10, 32, 24], [11, 35, 27],
        [12, 30, 22], [13, 40, 32], [14, 42, 34], [15, 47, 39], [16, 44, 36], [17, 48, 40],
        [18, 52, 44], [19, 54, 46], [20, 42, 34], [21, 55, 47], [22, 56, 48], [23, 57, 49],
        [24, 60, 52], [25, 50, 42], [26, 52, 44], [27, 51, 43], [28, 49, 41], [29, 53, 45],
        [30, 55, 47], [31, 60, 52], [32, 61, 53], [33, 59, 51], [34, 62, 54], [35, 65, 57],
        [36, 62, 54], [37, 58, 50], [38, 55, 47], [39, 61, 53], [40, 64, 56], [41, 65, 57],
        [42, 63, 55], [43, 66, 58], [44, 67, 59], [45, 69, 61], [46, 69, 61], [47, 70, 62],
        [48, 72, 64], [49, 68, 60], [50, 66, 58], [51, 65, 57], [52, 67, 59], [53, 70, 62],
        [54, 71, 63], [55, 72, 64], [56, 73, 65], [57, 75, 67], [58, 70, 62], [59, 68, 60],
        [60, 64, 56], [61, 60, 52], [62, 65, 57], [63, 67, 59], [64, 68, 60], [65, 69, 61],
        [66, 70, 62], [67, 72, 64], [68, 75, 67], [69, 80, 72]
      ]);
      var options = {
        hAxis: {
          title: 'Time'
        },
        vAxis: {
          title: 'Popularity'
        },
        colors: ['#a52714', '#097138']
      };
      var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
      chart.draw(data, options);
    }
</script>
  <div id="chart_div"></div>

But shows the following errors in browser console on loading the dashboard.

Uncaught ReferenceError: google is not defined
    at <anonymous>:2:33
    at DOMEval (web.assets_common.js:709)
    at domManip (web.assets_common.js:1060)
    at jQuery.fn.init.append (web.assets_common.js:1071)
    at Object.append (web.assets_common.js:3894)
    at Class._appendController (web.assets_backend.js:412)
    at Class._pushController (web.assets_backend.js:429)
    at web.assets_backend.js:415

and

Uncaught (in promise) TypeError: Cannot read property 'tooltip' of undefined
    at Class.<anonymous> (web.assets_common.js:4135)
    at Class.trigger (web.assets_common.js:3942)
    at Class.trigger (web.assets_common.js:3948)
    at Class.destroy (web.assets_common.js:3881)
    at Class.prototype.<computed> [as destroy] (web.assets_common.js:3860)
    at Class.trigger (web.assets_common.js:3942)
    at Class.trigger (web.assets_common.js:3948)
    at Class._pushController (web.assets_backend.js:429)
    at web.assets_backend.js:415

But it is perfectly working when I add it to a simple HTML file. The error occurs in Odoo only. Is there any way to fix this problem?