Use custom snapshot row translation to prevent Electron 1.6 reload crash

Adding a source map for the entire snapshot was expensive in terms of
memory and seemed to be triggering some sort of bug in Chromium when
reloading with the DevTools open.

The custom row translation relies on a much more compact representation
of the data and avoids the crash.

Signed-off-by: Nathan Sobo <nathan@github.com>

src/compile-cache.js

@@ -114,16 +114,19 @@ function writeCachedJavascript (relativeCachePath, code) {
 
 var INLINE_SOURCE_MAP_REGEXP = /\/\/[#@]\s*sourceMappingURL=([^'"\n]+)\s*$/mg
 
-let snapshotSourceMapConsumer
-if (global.isGeneratingSnapshot) {
-  // Warm up the source map consumer to efficiently translate positions when
-  // generating stack traces containing a file that was snapshotted.
-  const {SourceMapConsumer} = require('source-map')
-  snapshotSourceMapConsumer = new SourceMapConsumer(snapshotAuxiliaryData.sourceMap) // eslint-disable-line no-undef
-  snapshotSourceMapConsumer.originalPositionFor({line: 42, column: 0})
-}
-
 exports.install = function (resourcesPath, nodeRequire) {
+  const snapshotSourceMapConsumer = {
+    originalPositionFor ({line, column}) {
+      const {relativePath, row} = snapshotResult.translateSnapshotRow(line)
+      return {
+        column,
+        line: row,
+        source: path.join(resourcesPath, 'app', 'static', relativePath),
+        name: null
+      }
+    }
+  }
+
   sourceMapSupport.install({
     handleUncaughtExceptions: false,
 
@@ -132,10 +135,7 @@ exports.install = function (resourcesPath, nodeRequire) {
     // code from our cache directory.
     retrieveSourceMap: function (filePath) {
       if (filePath === '<embedded>') {
-        return {
-          map: snapshotSourceMapConsumer,
-          url: path.join(resourcesPath, 'app', 'static', 'index.js')
-        }
+        return {map: snapshotSourceMapConsumer}
       }
 
       if (!cacheDirectory || !fs.isFileSync(filePath)) {