Fixes issues that were causing runtests-browser to fail

src/compiler/program.ts

@@ -644,7 +644,8 @@ namespace ts {
             fileExists: fileName => sys.fileExists(fileName),
             readFile: fileName => sys.readFile(fileName),
             trace: (s: string) => sys.write(s + newLine),
-            directoryExists: directoryName => sys.directoryExists(directoryName)
+            directoryExists: directoryName => sys.directoryExists(directoryName),
+            getEnvironmentVariable: sys.getEnvironmentVariable
         };
     }
 
@@ -995,7 +996,7 @@ namespace ts {
             const start = new Date().getTime();
 
             // TODO(rbuckton): remove USE_TRANSFORMS condition when we switch to transforms permanently.
-            if (/^(y(es)?|t(rue|ransforms?)?|1|\+)$/i.test(sys.getEnvironmentVariable("USE_TRANSFORMS"))) {
+            if (/^(y(es)?|t(rue|ransforms?)?|1|\+)$/i.test(getEnvironmentVariable("USE_TRANSFORMS", host))) {
                 options.experimentalTransforms = true;
             }
 

src/compiler/sys.ts

@@ -74,6 +74,7 @@ namespace ts {
         readDirectory(path: string, extension?: string, exclude?: string[]): string[];
         watchFile?(path: string, callback: FileWatcherCallback): FileWatcher;
         watchDirectory?(path: string, callback: DirectoryWatcherCallback, recursive?: boolean): FileWatcher;
+        getEnvironmentVariable?(name: string): string;
     };
 
     export var sys: System = (function () {
@@ -632,9 +633,7 @@ namespace ts {
                 createDirectory: ChakraHost.createDirectory,
                 getExecutingFilePath: () => ChakraHost.executingFile,
                 getCurrentDirectory: () => ChakraHost.currentDirectory,
-                getEnvironmentVariable(name: string) {
-                    return "";
-                },
+                getEnvironmentVariable: ChakraHost.getEnvironmentVariable || ((name: string) => ""),
                 readDirectory: ChakraHost.readDirectory,
                 exit: ChakraHost.quit,
             };

src/compiler/types.ts

@@ -2805,6 +2805,7 @@ namespace ts {
          * 'throw new Error("NotImplemented")'
          */
         resolveModuleNames?(moduleNames: string[], containingFile: string): ResolvedModule[];
+        getEnvironmentVariable?(name: string): string;
     }
 
     /* @internal */

src/compiler/utilities.ts

@@ -169,6 +169,18 @@ namespace ts {
         return `${ file.fileName }(${ loc.line + 1 },${ loc.character + 1 })`;
     }
 
+    export function getEnvironmentVariable(name: string, host?: CompilerHost) {
+        if (host && host.getEnvironmentVariable) {
+            return host.getEnvironmentVariable(name);
+        }
+
+        if (sys && sys.getEnvironmentVariable) {
+            return sys.getEnvironmentVariable(name);
+        }
+
+        return "";
+    }
+
     export function getStartPosOfNode(node: Node): number {
         return node.pos;
     }

src/harness/harness.ts

@@ -1681,7 +1681,7 @@ namespace Harness {
     if (Error) (<any>Error).stackTraceLimit = 1;
 }
 
-if (ts.sys.tryEnableSourceMapsForHost && /^development$/i.test(ts.sys.getEnvironmentVariable("NODE_ENV"))) {
+if (ts.sys && ts.sys.tryEnableSourceMapsForHost && /^development$/i.test(ts.sys.getEnvironmentVariable("NODE_ENV"))) {
     ts.sys.tryEnableSourceMapsForHost();
 }