add a way to access the version string of the h/w implementation of EGL

we use a hidden egl extension. the version string is printed
in SF's dumpsys log.

Change-Id: I123eb4bde6de462bb2404c67b74d6d6219a48d6a
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 1b00e93..f38e948 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -65,6 +65,8 @@
 #define AID_GRAPHICS 1003
 #endif
 
+#define EGL_VERSION_HW_ANDROID  0x3143
+
 #define DISPLAY_COUNT       1
 
 namespace android {
@@ -1527,7 +1529,7 @@
          * Dump the layers in the purgatory
          */
 
-        const size_t purgatorySize =  mLayerPurgatory.size();
+        const size_t purgatorySize = mLayerPurgatory.size();
         snprintf(buffer, SIZE, "Purgatory state (%d entries)\n", purgatorySize);
         result.append(buffer);
         for (size_t i=0 ; i<purgatorySize ; i++) {
@@ -1548,6 +1550,12 @@
                 extensions.getRenderer(),
                 extensions.getVersion());
         result.append(buffer);
+
+        snprintf(buffer, SIZE, "EGL : %s\n",
+                eglQueryString(graphicPlane(0).getEGLDisplay(),
+                        EGL_VERSION_HW_ANDROID));
+        result.append(buffer);
+
         snprintf(buffer, SIZE, "EXTS: %s\n", extensions.getExtension());
         result.append(buffer);