Increase DEFAULT_CHUNK_SIZE to reduce transfer overhead

[domZippilli]

Fixes #86 by setting the DEFAULT_CHUNK_SIZE to 15MiB.

[elharo]

Looks like this breaks com.google.cloud.BaseWriteChannelTest

[codecov]

Codecov Report

Merging #87 into master will increase coverage by 0.14%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master      #87      +/-   ##
============================================
+ Coverage     66.32%   66.46%   +0.14%     
+ Complexity      367      362       -5     
============================================
  Files            34       34              
  Lines          1865     1858       -7     
  Branches        236      234       -2     
============================================
- Hits           1237     1235       -2     
+ Misses          526      521       -5     
  Partials        102      102

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/com/google/cloud/BaseWriteChannel.java	36.5% <ø> (ø)	18 <0> (ø)	⬇️
.../com/google/cloud/MonitoredResourceDescriptor.java	83.76% <0%> (-0.28%)	20% <0%> (-4%)
...a/com/google/cloud/testing/BaseEmulatorHelper.java	31.21% <0%> (-0.22%)	5% <0%> (ø)
...src/main/java/com/google/cloud/ServiceOptions.java	41.66% <0%> (+0.75%)	29% <0%> (-1%)	⬇️
...re/src/main/java/com/google/cloud/RetryHelper.java	53.84% <0%> (+3.84%)	2% <0%> (ø)	⬇️

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[frankyn]

LGTM. Thanks @domZippilli!

[domZippilli]

Hey just wanted to check in -- are there any steps I need to take to move this forward?

[elharo]

@frankyn FYI, you need to select the approve button in Github. Unlike google3, LGTM in a comment doesn't suffice.

[frankyn]

I did approve, but my approval doesn't count IIUC. Also I can't merge, could you help merge the PR as well @elharo?