Fix flaky disk cache size test

This CL fixes the flaky disk cache size test. The particular
flakiness resulted from off-by-one errors e.g.
Expected: (max_file_size_scaled) <= (2 * max_file_size),
actual: 55319511 vs 55319510
which occurred because file size is computed as (total cache size/8).

The fix however not just accounts for off-by-one errors but removes the
check completely as the total cache size is dependent on the available
disk space which cannot be guaranteed to be the same between the 2
invocations of VerifyDiskCacheSize.

Bug: 1162434
Change-Id: I510eed9ca0ed90e12e953910f7f699be74e10b14
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625350Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Commit-Queue: Shivani Sharma <shivanisha@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842715}

services/network/network_context_unittest.cc

@@ -954,13 +954,14 @@ class DiskCacheSizeTest : public NetworkContextTest {
 TEST_F(DiskCacheSizeTest, DiskCacheSize) {
   int64_t max_file_size = VerifyDiskCacheSize();
 
-  // Scale to 200%. The size should be twice of |max_file_size| but
-  // since max size is capped on 20% of available size, checking for the size to
-  // be between max_file_size and max_file_size*2.
   int64_t max_file_size_scaled = VerifyDiskCacheSize(200);
 
+  // After scaling to 200%, the size will in most cases be twice of
+  // |max_file_size| but it is dependent on the available size, and since we
+  // cannot guarantee available size to be the same between the 2 runs to
+  // VerifyDiskCacheSize(), only checking for the scaled size to be >=
+  // max_file_size.
   EXPECT_GE(max_file_size_scaled, max_file_size);
-  EXPECT_LE(max_file_size_scaled, 2 * max_file_size);
 }
 
 // This makes sure that network_session_configurator::ChooseCacheType is