On Android uses system properties instead of environment variables.

Source/bindings/dart/DartController.cpp

Index: Source/bindings/dart/DartController.cpp
===================================================================
--- Source/bindings/dart/DartController.cpp	(revision 1475)
+++ Source/bindings/dart/DartController.cpp	(working copy)
@@ -30,6 +30,11 @@
 #include "config.h"
 #include "bindings/dart/DartController.h"
 
+#if OS(ANDROID)
+#include <sys/system_properties.h>
+#endif
+
+
 #include "DartDocument.h"
 #include "DartWindow.h"
 #include "HTMLNames.h"
@@ -179,7 +184,14 @@
     domData->setTypedDataLibrary(Dart_NewPersistentHandle(typedData));
 
     // Setup configuration closures
-    const char * const printClosure = getenv("DART_FORWARDING_PRINT") ?
+#if OS(ANDROID)
+    char forwardingProperty[PROP_VALUE_MAX];
+    int propLen = __system_property_get("DART_FORWARDING_PRINT", &forwardingProperty[0]);
+    bool forwardPrint = propLen > 0;
+#else
+    bool forwardPrint = getenv("DART_FORWARDING_PRINT");
+#endif
+    const char * const printClosure = forwardPrint ?
         "_forwardingPrintClosure" :
         (isDOMEnabled ?  "_printClosure" : "_pureIsolatePrintClosure");
     copyValue(html, printClosure, "dart:_collection-dev", 0, "_printClosure");