Show coverage percentages in table of contents

Summary:
Rough cut -- this needs style / color / tooltips, etc. Show raw coverage and "modified coverage" (coverage on lines you touched) in the table of contents.

https://secure.phabricator.com/file/data/id3apce5p5gevkee6tg2/PHID-FILE-kxcxlbsej454t4xiht2o/Screen_Shot_2012-03-12_at_3.30.30_PM.png

Test Plan: See screenshot above.

Reviewers: tuomaspelkonen, btrahan, zeeg

Reviewed By: tuomaspelkonen

CC: aran, epriestley

Maniphest Tasks: T965

Differential Revision: https://secure.phabricator.com/D1864

src/applications/differential/parser/changeset/DifferentialChangesetParser.php

@@ -1714,4 +1714,49 @@ class DifferentialChangesetParser {
     return array($range_s, $range_e, $mask);
   }
 
+  /**
+   * Render "modified coverage" information; test coverage on modified lines.
+   * This synthesizes diff information with unit test information into a useful
+   * indicator of how well tested a change is.
+   */
+  public function renderModifiedCoverage() {
+    $na = '<em>-</em>';
+
+    if (!$this->coverage) {
+      return $na;
+    }
+
+    $covered = 0;
+    $not_covered = 0;
+
+    foreach ($this->new as $k => $new) {
+      if (!$new['line']) {
+        continue;
+      }
+
+      if (!$new['type']) {
+        continue;
+      }
+
+      if (empty($this->coverage[$new['line'] - 1])) {
+        continue;
+      }
+
+      switch ($this->coverage[$new['line']]) {
+        case 'C':
+          $covered++;
+          break;
+        case 'U':
+          $not_covered++;
+          break;
+      }
+    }
+
+    if (!$covered && !$not_covered) {
+      return $na;
+    }
+
+    return sprintf('%d%%', 100 * ($covered / ($covered + $not_covered)));
+  }
+
 }