[wasm] Bump wasm function size limit to 7654321 bytes.

Pending the outcome of the discussion on the GitHub issue:
https://github.com/WebAssembly/design/issues/1138

R=clemensh@chromium.org,ahaas@chromium.org

Bug: 
Change-Id: I54a218a93c24cb221b9f0195e2b1abbe6208d8e2
Reviewed-on: https://chromium-review.googlesource.com/735343Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48907}

src/wasm/wasm-limits.h

@@ -29,7 +29,7 @@ constexpr size_t kV8MaxWasmDataSegments = 100000;
 constexpr size_t kV8MaxWasmMemoryPages = 32767;  // ~ 2 GiB
 constexpr size_t kV8MaxWasmStringSize = 100000;
 constexpr size_t kV8MaxWasmModuleSize = 1024 * 1024 * 1024;  // = 1 GiB
-constexpr size_t kV8MaxWasmFunctionSize = 128 * 1024;
+constexpr size_t kV8MaxWasmFunctionSize = 7654321;
 constexpr size_t kV8MaxWasmFunctionLocals = 50000;
 constexpr size_t kV8MaxWasmFunctionParams = 1000;
 constexpr size_t kV8MaxWasmFunctionMultiReturns = 1000;