[fuchsia] Implement no-op TtsPlatform.

This prevents a browser crash when a page attempts to use the Web
Speech API.

Bug: 1019511
Change-Id: Ie369adc51dc4fa8228bd9df5a1b102dffd44daa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888105
Reviewed-by: David Dorwin <[email protected]>
Reviewed-by: David Tseng <[email protected]>
Commit-Queue: Fabrice de Gans-Riberi <[email protected]>
Cr-Commit-Position: refs/heads/master@{#711528}
diff --git a/content/browser/BUILD.gn b/content/browser/BUILD.gn
index 352901c9..5d1e281 100644
--- a/content/browser/BUILD.gn
+++ b/content/browser/BUILD.gn
@@ -2035,7 +2035,10 @@
   }
 
   if (is_fuchsia) {
-    sources += [ "child_process_launcher_helper_fuchsia.cc" ]
+    sources += [
+      "child_process_launcher_helper_fuchsia.cc",
+      "speech/tts_fuchsia.cc",
+    ]
     deps += [ "//third_party/fuchsia-sdk/sdk:zx" ]
   } else if (is_posix) {
     sources += [