Revert "Fix fuschia build."

This reverts commit 9ae967fe.

Reason for revert: Breaks Chromium, see https://crrev.com/c/741484. Will also revert https://crrev.com/c/738890 after this.

Original change's description:
> Fix fuschia build.
> 
> Bug:chromium:756050
> Change-Id: Ib65c9c4c19266eb1c6119367397be0769cfcc7a1
> 
> TBR=ulan@chromium.org
> 
> Change-Id: Ib65c9c4c19266eb1c6119367397be0769cfcc7a1
> Reviewed-on: https://chromium-review.googlesource.com/740083
> Reviewed-by: Bill Budge <bbudge@chromium.org>
> Commit-Queue: Bill Budge <bbudge@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48984}

TBR=bbudge@chromium.org,ulan@chromium.org,mlippautz@chromium.org,scottmg@chromium.org

Change-Id: Ie4db6aeb231fe919969a19bbe51589e108127378
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:756050
Reviewed-on: https://chromium-review.googlesource.com/741761Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49002}

src/base/platform/platform-posix.cc

@@ -73,7 +73,6 @@ bool g_hard_abort = false;
 
 const char* g_gc_fake_mmap = nullptr;
 
-#if !V8_OS_FUCHSIA
 #if V8_OS_MACOSX
 // kMmapFd is used to pass vm_alloc flags to tag the region with the user
 // defined tag 255 This helps identify V8-allocated regions in memory analysis
@@ -96,7 +95,6 @@ int GetProtectionFromMemoryPermission(OS::MemoryPermission access) {
   }
   UNREACHABLE();
 }
-#endif  // !V8_OS_FUCHSIA
 
 }  // namespace