Consider embedded input source map in file coverage

When locating the source map, use the source map included in the
file coverage whenever possible. Closes SitePen#2 but requires
istanbuljs-archived-repos/istanbul-lib-instrument#23

lib/remap.js

@@ -231,38 +231,43 @@ define([
 				else {
 					codeIsArray = false;
 				}
-				var match = sourceMapRegEx.exec(jsText);
-				var sourceMapDir = path.dirname(filePath);
-				var rawSourceMap;
-
-				if (!match && !codeFromFile) {
-					codeIsArray = false;
-					jsText = readFile(filePath);
-					match = sourceMapRegEx.exec(jsText);
-				}
 
-				if (match) {
-					if (match[1]) {
-						rawSourceMap = JSON.parse((new Buffer(match[2], 'base64').toString('utf8')));
+				var rawSourceMap;
+				var sourceMapDir = path.dirname(filePath);
+				if (fileCoverage.inputSourceMap) {
+				    rawSourceMap = fileCoverage.inputSourceMap;
+				} else {
+					var match = sourceMapRegEx.exec(jsText);
+
+					if (!match && !codeFromFile) {
+						codeIsArray = false;
+						jsText = readFile(filePath);
+						match = sourceMapRegEx.exec(jsText);
 					}
-					else {
-						var sourceMapPath = path.join(sourceMapDir, match[2]);
-						rawSourceMap = readJSON(sourceMapPath);
-						sourceMapDir = path.dirname(sourceMapPath);
+
+					if (match) {
+						if (match[1]) {
+							rawSourceMap = JSON.parse((new Buffer(match[2], 'base64').toString('utf8')));
+						}
+						else {
+							var sourceMapPath = path.join(sourceMapDir, match[2]);
+							rawSourceMap = readJSON(sourceMapPath);
+							sourceMapDir = path.dirname(sourceMapPath);
+						}
 					}
-				}
 
-				if (!match || !rawSourceMap) {
-					/* We couldn't find a source map, so will copy coverage after warning. */
-					warn(new Error('Could not find source map for: "' + filePath + '"'));
-					try {
-						fileCoverage.code = String(fs.readFileSync(filePath)).split('\n');
-					}
-					catch (error) {
-						warn(new Error('Could find source for : "' + filePath + '"'));
+					if (!match || !rawSourceMap) {
+						/* We couldn't find a source map, so will copy coverage after warning. */
+						warn(new Error('Could not find source map for: "' + filePath + '"'));
+						try {
+							fileCoverage.code = String(fs.readFileSync(filePath)).split('\n');
+						}
+						catch (error) {
+							warn(new Error('Could find source for : "' + filePath + '"'));
+						}
+						srcCoverage[filePath] = fileCoverage;
+						return;
 					}
-					srcCoverage[filePath] = fileCoverage;
-					return;
 				}
 
 				sourceMapDir = options.basePath || sourceMapDir;