LazyLoad: Change default number of images to load eagerly to 0.

The load-first-K-images-eagerly optimization (https://crbug.com/996963),
which causes Automatic LazyLoad to avoid deferring the first K images
encountered by the parser, should default to zero. This way, the default
behavior will match the previous behavior without this optimization, and
it'll be easier to experiment with other values as needed.

Bug: 1086726
Change-Id: I806008bba93fee471a596f67842f5db1b3f0e0f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216805
Auto-Submit: Scott Little <sclittle@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772150}

third_party/blink/renderer/core/frame/settings.json5

@@ -1040,22 +1040,22 @@
     },
     {
       name: "lazyImageFirstKFullyLoadSlow2G",
-      initial: 12,
+      initial: 0,
       type: "int",
     },
     {
       name: "lazyImageFirstKFullyLoad2G",
-      initial: 10,
+      initial: 0,
       type: "int",
     },
     {
       name: "lazyImageFirstKFullyLoad3G",
-      initial: 8,
+      initial: 0,
       type: "int",
     },
     {
       name: "lazyImageFirstKFullyLoad4G",
-      initial: 6,
+      initial: 0,
       type: "int",
     },