This fixes the uncommon fallback when Compiler::CompileOptimized fails
creating optimized code and also the underlying SharedFunctionInfo is
not compiled. We make sure not to uselessly regenerate the bytecode.

R=rmcilroy@chromium.org
BUG=chromium:639753

Review-Url: https://codereview.chromium.org/2261123002
Cr-Commit-Position: refs/heads/master@{#38776}