Skip BindGroupTests.ReusedUBO and UBOSamplerAndTexture on Metal

BindGroupTests.ReusedUBO and BindGroupTests.UBOSamplerAndTexture fail on
Metal so we have to skip them temporarily.

BUG=dawn:33

Change-Id: I2875dab6d856eb207ee5b785ddf160df2cb9fd5b
Reviewed-on: https://dawn-review.googlesource.com/c/2240
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/tests/end2end/BindGroupTests.cpp b/src/tests/end2end/BindGroupTests.cpp
index 39cdcbe..429abda 100644
--- a/src/tests/end2end/BindGroupTests.cpp
+++ b/src/tests/end2end/BindGroupTests.cpp
@@ -83,6 +83,9 @@
 // It contains a transformation matrix for the VS and the fragment color for the FS.
 // These must result in different register offsets in the native APIs.
 TEST_P(BindGroupTests, ReusedUBO) {
+    // TODO(jiawei.shao@intel.com): find out why this test fails on Metal
+    DAWN_SKIP_TEST_IF(IsMetal());
+
     utils::BasicRenderPass renderPass = utils::CreateBasicRenderPass(device, kRTSize, kRTSize);
 
     dawn::ShaderModule vsModule = utils::CreateShaderModule(device, dawn::ShaderStage::Vertex, R"(
@@ -169,6 +172,9 @@
 // In D3D12 for example, these different types of bindings end up in different namespaces, but the register
 // offsets used must match between the shader module and descriptor range.
 TEST_P(BindGroupTests, UBOSamplerAndTexture) {
+    // TODO(jiawei.shao@intel.com): find out why this test fails on Metal
+    DAWN_SKIP_TEST_IF(IsMetal());
+
     utils::BasicRenderPass renderPass = utils::CreateBasicRenderPass(device, kRTSize, kRTSize);
 
     dawn::ShaderModule vsModule = utils::CreateShaderModule(device, dawn::ShaderStage::Vertex, R"(