Add missing sourcesContent & mappings test cases

Covers a few additional error cases that were actually missing from the test
coverage.

Author: takikawa

resources/mappings-missing.js

@@ -42,6 +42,13 @@
       "sourceMapFile": "version-too-low.js.map",
       "sourceMapIsValid": false
     },
+    {
+      "name": "mappingsMissing",
+      "description": "Test a source map that is missing a necessary mappings field",
+      "baseFile": "mappings-missing.js",
+      "sourceMapFile": "mappings-missing.js.map",
+      "sourceMapIsValid": false
+    },
     {
       "name": "sourcesMissing",
       "description": "Test a source map that is missing a necessary sources field",
@@ -70,6 +77,34 @@
       "sourceMapFile": "sources-not-string-or-null.js.map",
       "sourceMapIsValid": false
     },
+    {
+      "name": "sourcesContentMissing",
+      "description": "Test a source map that is missing an optional sourcesContent field",
+      "baseFile": "sources-content-missing.js",
+      "sourceMapFile": "sources-content-missing.js.map",
+      "sourceMapIsValid": true
+    },
+    {
+      "name": "sourcesContentNotAList1",
+      "description": "Test a source map with a sourcesContent field that is not a valid list (string)",
+      "baseFile": "sources-content-not-a-list-1.js",
+      "sourceMapFile": "sources-content-not-a-list-1.js.map",
+      "sourceMapIsValid": false
+    },
+    {
+      "name": "sourcesContentNotAList2",
+      "description": "Test a source map with a sourcesContent field that is not a valid list (object)",
+      "baseFile": "sources-content-not-a-list-2.js",
+      "sourceMapFile": "sources-content-not-a-list-2.js.map",
+      "sourceMapIsValid": false
+    },
+    {
+      "name": "sourcesContentNotStringOrNull",
+      "description": "Test a source map with a sourcesContent list that has non-string and non-null items",
+      "baseFile": "sources-not-string-or-null.js",
+      "sourceMapFile": "sources-content-not-string-or-null.js.map",
+      "sourceMapIsValid": false
+    },
     {
       "name": "sourcesAndSourcesContentBothNull",
       "description": "Test a source map that has both null sources and sourcesContent entries",