Fix BufferLimitConfig test for low memory devices

This commit fixes the BufferLimitConfig content unittest by accounting
for low memory devices.

When a device has 1 GB or less of RAM,
BackgroundTracingConfigImpl::GetMaximumTraceBufferSizeKb() returns the
low RAM buffer size instead of mobile network buffer size for Android.

This commit updates the BufferLimitConfig test expectations to handle
that code path properly.

TEST=out/Debug/bin/run_content_unittests --num_retries=0
       -f BackgroundTracingConfigTest.BufferLimitConfig

Bug: 1038539
Change-Id: I53622041b06c012b9b3b06dc9df49b8587f57b4f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1983669Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#731773}

content/browser/tracing/background_tracing_config_unittest.cc

@@ -6,6 +6,7 @@
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
+#include "base/system/sys_info.h"
 #include "base/values.h"
 #include "build/build_config.h"
 #include "content/browser/tracing/background_tracing_config_impl.h"
@@ -690,7 +691,11 @@ TEST_F(BackgroundTracingConfigTest, BufferLimitConfig) {
 
   notifier.set_type(net::NetworkChangeNotifier::CONNECTION_2G);
 #if defined(OS_ANDROID)
-  EXPECT_EQ(300u, config->GetTraceConfig().GetTraceBufferSizeInKb());
+  int64_t ram_mb = base::SysInfo::AmountOfPhysicalMemoryMB();
+  size_t expected_trace_buffer_size =
+      (ram_mb > 0 && ram_mb <= 1024) ? 800u : 300u;
+  EXPECT_EQ(expected_trace_buffer_size,
+            config->GetTraceConfig().GetTraceBufferSizeInKb());
   EXPECT_EQ(600u, config->GetTraceUploadLimitKb());
 #endif