Revert of Make the Sk GL context class an abstract base class

src/gpu/gl/angle/SkANGLEGLContext.cpp

Index: src/gpu/gl/angle/SkANGLEGLContext.cpp
diff --git a/src/gpu/gl/angle/SkANGLEGLContext.cpp b/src/gpu/gl/angle/SkANGLEGLContext.cpp
index 4914ba55333d70df73ccac437b940ac0db7b6085..81fccebba0cf08a9932d67a1a88abe1be89d0f41 100644
--- a/src/gpu/gl/angle/SkANGLEGLContext.cpp
+++ b/src/gpu/gl/angle/SkANGLEGLContext.cpp
@@ -7,6 +7,21 @@
  */
 
 #include "gl/SkANGLEGLContext.h"
+
+SkANGLEGLContext::AutoContextRestore::AutoContextRestore() {
+    fOldEGLContext = eglGetCurrentContext();
+    fOldDisplay = eglGetCurrentDisplay();
+    fOldSurface = eglGetCurrentSurface(EGL_DRAW);
+
+}
+
+SkANGLEGLContext::AutoContextRestore::~AutoContextRestore() {
+    if (fOldDisplay) {
+        eglMakeCurrent(fOldDisplay, fOldSurface, fOldSurface, fOldEGLContext);
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
 
 SkANGLEGLContext::SkANGLEGLContext()
     : fContext(EGL_NO_CONTEXT)