Speed up rendering of large docs in doc table (#9014) (#9150)

Back in 2014 a utility was added to insert <wbr> (word break opportunity)
tags into doc table fields to improve their display in the browser. This
utility looped over every character in _source when it was selected as a
column in the doc table, which it was be default. That really started to
slow things down when displaying large docs. We can maintain similar word
breaking without adding <wbr> tags by adding some css styles that
do essentially the same job. word-break: break-word gives us the best
formatting but it's not a part of the standard yet (see link below) so I
provided an almost-as-good fallback with break-all.

https://bugs.chromium.org/p/chromium/issues/detail?id=492202#c21

Fixes #6328
Related #1993

src/ui/public/doc_table/components/table_row.js

@@ -1,7 +1,6 @@
 define(function (require) {
   let _ = require('lodash');
   let $ = require('jquery');
-  let addWordBreaks = require('ui/utils/add_word_breaks');
   let module = require('ui/modules').get('app/discover');
 
   require('ui/highlight');
@@ -150,18 +149,14 @@ define(function (require) {
         /**
          * Fill an element with the value of a field
          */
-        function _displayField(row, fieldName, breakWords) {
+        function _displayField(row, fieldName, truncate) {
           let indexPattern = $scope.indexPattern;
           let text = indexPattern.formatField(row, fieldName);
 
-          if (breakWords) {
-            text = addWordBreaks(text, MIN_LINE_LENGTH);
-
-            if (text.length > MIN_LINE_LENGTH) {
-              return truncateByHeightTemplate({
-                body: text
-              });
-            }
+          if (truncate && text.length > MIN_LINE_LENGTH) {
+            return truncateByHeightTemplate({
+              body: text
+            });
           }
 
           return text;

src/ui/public/doc_table/doc_table.less

@@ -6,6 +6,16 @@ doc-table {
 
   .discover-table-datafield {
     white-space: pre-wrap;
+
+    // break-word is what we really want but it hasn't been added to the standard and adopted by all browsers yet,
+    // so we provide break-all as a fallback
+    word-break: break-all;
+    word-break: break-word;
+  }
+
+  .discover-table-sourcefield {
+    word-break: break-all;
+    word-break: break-word;
   }
 
   .loading {