glbench: add ContextTest and GLInterfaceTest base class

Add a test class, ContextTest, to test context switching.  This is
similar enough to SwapTest so create a base class GLInterfaceTest that
contains code that is common to both.  ContextTest and SwapTest classes
derive from GLInterfaceTest:

                 GLInterfaceTest
                       |
              +--------+--------+
              |                 |
         ContextTest         SwapTest

BUG=chromium-os:36746,chromium-os:36750
TEST=emerge autotest-deps-glbench, run: "glbench -tests swap:context"

Change-Id: Ibc5e506c61bdbca75a81e04ee6ca70af310c345c
Signed-off-by: Simon Que <sque@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39886
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
diff --git a/client/deps/glbench/src/main.cc b/client/deps/glbench/src/main.cc
index cc6a50a..642665d 100644
--- a/client/deps/glbench/src/main.cc
+++ b/client/deps/glbench/src/main.cc
@@ -62,10 +62,9 @@
     return 1;
   }
 
-  g_main_gl_interface->InitContext();
   printf("# board_id: %s - %s\n",
          glGetString(GL_VENDOR), glGetString(GL_RENDERER));
-  g_main_gl_interface->DestroyContext();
+  g_main_gl_interface->Cleanup();
 
   if (argc == 1) {
     printf("# Usage: %s [-save [-outdir=<directory>]] to save images\n", argv[0]);
@@ -80,6 +79,7 @@
   base::SplitString(FLAGS_tests, ':', &enabled_tests);
   glbench::TestBase* tests[] = {
     glbench::GetSwapTest(),
+    glbench::GetContextTest(),
     glbench::GetClearTest(),
     glbench::GetFillRateTest(),
     glbench::GetWindowManagerCompositingTest(false),
@@ -99,13 +99,13 @@
     for (unsigned int i = 0; i < arraysize(tests); i++) {
       if (!test_is_enabled(tests[i], enabled_tests))
         continue;
-      if (!g_main_gl_interface->InitContext()) {
-        printf("InitContext failed\n");
+      if (!g_main_gl_interface->Init()) {
+        printf("Initialize failed\n");
         return 1;
       }
       glbench::ClearBuffers();
       tests[i]->Run();
-      g_main_gl_interface->DestroyContext();
+      g_main_gl_interface->Cleanup();
     }
   } while (GetUTime() < done);