Disable new warning -Wenum-float-conversion in blink build config

Change-Id: I34125effba684908abb1a6983b641419d63242b6
Bug: 1035977
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976019
Commit-Queue: Amy Huang <akhuang@google.com>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726533}

third_party/blink/renderer/BUILD.gn

@@ -52,6 +52,7 @@ config("inside_blink") {
     if (llvm_force_head_revision) {
       cflags += [
         "-Wno-enum-enum-conversion",
+        "-Wno-enum-float-conversion",
       ]
     }
   }