Restore earlyouts in SignalTests on Windows for IPC flavour of the tests

These tests fail to set up correctly on Windows, so running the tests
just crashes. Restore the early outs with an ifdef for windows so we
document where the early out will happen, along with comments.

R=kbr@chromium.org, piman@chromium.org
BUG=595823, 584497

Review URL: https://codereview.chromium.org/1812033002

Cr-Commit-Position: refs/heads/master@{#381802}

content/browser/gpu/gpu_ipc_browsertests.cc

@@ -30,6 +30,8 @@ const content::CauseForGpuLaunch kInitCause =
 class ContextTestBase : public content::ContentBrowserTest {
  public:
   void SetUpOnMainThread() override {
+    // This may leave the provider_ null in some cases, so tests need to early
+    // out.
     if (!content::BrowserGpuChannelHostFactory::CanUseForTesting())
       return;
 
@@ -71,8 +73,8 @@ class ContextTestBase : public content::ContentBrowserTest {
   }
 
  protected:
-  gpu::gles2::GLES2Interface* gl_;
-  gpu::ContextSupport* context_support_;
+  gpu::gles2::GLES2Interface* gl_ = nullptr;
+  gpu::ContextSupport* context_support_ = nullptr;
 
  private:
   scoped_refptr<content::ContextProviderCommandBuffer> provider_;

content/common/gpu/client/gpu_context_tests.h

@@ -42,6 +42,13 @@ class SignalTest : public ContextTestBase {
 };
 
 CONTEXT_TEST_F(SignalTest, BasicSignalSyncTokenTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   const GLuint64 fence_sync = gl_->InsertFenceSyncCHROMIUM();
   gl_->ShallowFlushCHROMIUM();
 
@@ -52,6 +59,13 @@ CONTEXT_TEST_F(SignalTest, BasicSignalSyncTokenTest) {
 };
 
 CONTEXT_TEST_F(SignalTest, EmptySignalSyncTokenTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   // Signalling something that doesn't exist should run the callback
   // immediately.
   gpu::SyncToken sync_token;
@@ -59,6 +73,13 @@ CONTEXT_TEST_F(SignalTest, EmptySignalSyncTokenTest) {
 };
 
 CONTEXT_TEST_F(SignalTest, InvalidSignalSyncTokenTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   // Signalling something that doesn't exist should run the callback
   // immediately.
   gpu::SyncToken sync_token(gpu::CommandBufferNamespace::GPU_IO, 0,
@@ -68,6 +89,13 @@ CONTEXT_TEST_F(SignalTest, InvalidSignalSyncTokenTest) {
 };
 
 CONTEXT_TEST_F(SignalTest, BasicSignalQueryTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   unsigned query;
   gl_->GenQueriesEXT(1, &query);
   gl_->BeginQueryEXT(GL_COMMANDS_ISSUED_CHROMIUM, query);
@@ -78,6 +106,13 @@ CONTEXT_TEST_F(SignalTest, BasicSignalQueryTest) {
 };
 
 CONTEXT_TEST_F(SignalTest, SignalQueryUnboundTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   GLuint query;
   gl_->GenQueriesEXT(1, &query);
   TestSignalQuery(query);
@@ -85,6 +120,13 @@ CONTEXT_TEST_F(SignalTest, SignalQueryUnboundTest) {
 };
 
 CONTEXT_TEST_F(SignalTest, InvalidSignalQueryUnboundTest) {
+#if defined(OS_WIN)
+  // The IPC version of ContextTestBase::SetUpOnMainThread does not succeed on
+  // some platforms.
+  if (!gl_)
+    return;
+#endif
+
   // Signalling something that doesn't exist should run the callback
   // immediately.
   TestSignalQuery(928729087);