Added tests to check that WebGL extensions are available.

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

Index: content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
diff --git a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
index 7ee1229411ff293c4b883946930b483ed75594dc..57cb4f71f8c5cda3f3eeb78734bf71a493902483 100644
--- a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
@@ -10,6 +10,26 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
     super(WebGL2ConformanceExpectations, self).__init__(conformance_path)
 
   def SetExpectations(self):
+    # ===================================
+    # Extension availability expectations
+    # ===================================
+    # It's expected that not all extensions will be available on all platforms.
+    # Having a test listed here is not necessarily a problem.
+
+    self.Fail('WebglExtension.EXT_color_buffer_float',
+        ['win', 'mac', 'linux'])
+    self.Fail('WebglExtension.WEBGL_compressed_texture_astc',
+        ['win', 'mac', 'linux'])
+    self.Fail('WebglExtension.WEBGL_compressed_texture_atc',
+        ['win', 'mac', 'linux'])
+    self.Fail('WebglExtension.WEBGL_compressed_texture_etc1',
+        ['mac', 'linux'])
+    self.Fail('WebglExtension.WEBGL_compressed_texture_pvrtc',
+        ['win', 'mac', 'linux'])
+
+    # ========================
+    # Conformance expectations
+    # ========================
     # All platforms.
     self.Skip('deqp/functional/gles3/builtinprecision*.html', bug=483282)
     self.Skip('deqp/functional/gles3/draw.html', bug=483282)