Disable GLES20Canvas on emu w/o native GL

When the emulator is run without '-gpu on', GLES20 isn't supported,
so claiming GLES20Canvas is available will lead to catastrophic
failure. This change makes GLES20Canvas available when compiled in
and either not running on the emulator, or running on the emulator
with native GL acceleration enabled.

Change-Id: I89c944f9e3c9585224f5aa0877335ea48ea4a468

Author: critsec

core/jni/android_view_GLES20Canvas.cpp

@@ -23,6 +23,7 @@
 #include <nativehelper/JNIHelp.h>
 #include <android_runtime/AndroidRuntime.h>
 #include <android_runtime/android_graphics_SurfaceTexture.h>
+#include <cutils/properties.h>
 #include <utils/ResourceTypes.h>
 
 #include <gui/SurfaceTexture.h>
@@ -736,7 +737,15 @@ static jboolean android_view_GLES20Canvas_copyLayer(JNIEnv* env, jobject clazz,
 
 static jboolean android_view_GLES20Canvas_isAvailable(JNIEnv* env, jobject clazz) {
 #ifdef USE_OPENGL_RENDERER
-    return JNI_TRUE;
+    char prop[PROPERTY_VALUE_MAX];
+    if (property_get("ro.kernel.qemu", prop, NULL) == 0) {
+        // not in the emulator
+        return JNI_TRUE;
+    }
+    // In the emulator this property will be set to 1 when hardware GLES is
+    // enabled, 0 otherwise. On old emulator versions it will be undefined.
+    property_get("ro.kernel.qemu.gles", prop, "0");
+    return atoi(prop) == 1 ? JNI_TRUE : JNI_FALSE;
 #else
     return JNI_FALSE;
 #endif