Use correct path escape on Windows, for Process.

runtime/bin/process_patch.dart

Index: runtime/bin/process_patch.dart
diff --git a/runtime/bin/process_patch.dart b/runtime/bin/process_patch.dart
index b957bacb4c6cbd5909c5f9b554edf33b27da692a..729a7b5f492df88269d41130423090dab933aac2 100644
--- a/runtime/bin/process_patch.dart
+++ b/runtime/bin/process_patch.dart
@@ -140,7 +140,6 @@ class _ProcessImpl extends NativeFieldWrapperClass1 implements Process {
       shellArguments.add('/c');
       shellArguments.add(executable);
       for (var arg in arguments) {
-        arg = arg.replaceAll('"', r'\"');
         shellArguments.add(arg);
       }
     } else {
@@ -159,7 +158,9 @@ class _ProcessImpl extends NativeFieldWrapperClass1 implements Process {
 
   String _windowsArgumentEscape(String argument) {
     var result = argument;
-    if (argument.contains('\t') || argument.contains(' ')) {
+    if (argument.contains('\t') ||
+        argument.contains(' ') ||
+        argument.contains('"')) {
       // Produce something that the C runtime on Windows will parse
       // back as this string.