[Fuchsia] Disable StackTraceTest.OutputToStream on official builds.

Backtrace generation doesn't work for optimized official builds, so the
StackTraceTest test is disabled for that case.

Bug: 999737
Change-Id: If7e395d82bd77ba47cb63d33cfab1b66711f627a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779566
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Auto-Submit: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692287}

base/debug/stack_trace_unittest.cc

@@ -31,11 +31,20 @@ typedef MultiProcessTest StackTraceTest;
 typedef testing::Test StackTraceTest;
 #endif
 
+// TODO(https://crbug.com/999737): Rewrite this test for better clarity and
+// correctness.
 // Note: On Linux, this test currently only fully works on Debug builds.
 // See comments in the #ifdef soup if you intend to change this.
 #if defined(OS_WIN)
+
 // Always fails on Windows: crbug.com/32070
 #define MAYBE_OutputToStream DISABLED_OutputToStream
+
+#elif defined(OS_FUCHSIA) && defined(OFFICIAL_BUILD)
+
+// Backtraces aren't supported by Fuchsia release-optimized builds.
+#define MAYBE_OutputToStream DISABLED_OutputToStream
+
 #else
 #define MAYBE_OutputToStream OutputToStream
 #endif