Create chrome_branch_deps.json for branch 6490.

Change-Id: I5975ea340fe2862b21025f43fd14a89c66032662
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5546661
Bot-Commit: Chrome Release Bot (LUCI) <chrome-official-brancher@chops-service-accounts.iam.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/6490@{#1}
Cr-Branched-From: c517559-refs/heads/main@{#1303179}

chrome/chrome_branch_deps.json

@@ -0,0 +1,17 @@
+{
+  "src": "refs/branch-heads/6490",
+  "src:src/clank": "refs/heads/chromium/6490",
+  "src:src/components/optimization_guide/internal": "refs/heads/chromium/6490",
+  "src:src/internal": "refs/heads/chromium/6490",
+  "src:src/ios_internal": "refs/heads/chromium/6490",
+  "src:src/third_party/angle": "refs/heads/chromium/6490",
+  "src:src/third_party/dawn": "refs/heads/chromium/6490",
+  "src:src/third_party/devtools-frontend-internal": "refs/heads/chromium/6490",
+  "src:src/third_party/devtools-frontend-internal:devtools-frontend": "refs/heads/chromium/6490",
+  "src:src/third_party/devtools-frontend/src": "refs/heads/chromium/6490",
+  "src:src/third_party/instrumented_libs": "refs/heads/chromium/6490",
+  "src:src/third_party/pdfium": "refs/heads/chromium/6490",
+  "src:src/third_party/vulkan-deps": "refs/heads/chromium/6490",
+  "src:src/third_party/webrtc": "refs/branch-heads/6490",
+  "src:src/v8": "refs/heads/chromium/6490"
+}