supersize: Don't cluster by default. Make Diff() accept only SizeInfo.

tools/binary_size/libsupersize/testdata/Console.golden

 # Show pydoc for main types:
 import models
 help(models)
 
 # Show all attributes of all symbols & per-section totals:
 Print(size_info, verbose=True)
 
 # Show two levels of .text, grouped by first two subdirectories
 text_syms = size_info.symbols.WhereInSection("t")
 by_path = text_syms.GroupBySourcePath(depth=2)
@@ skipping 23 matching lines @@
     map_file_name=../test.map
 
 Section Sizes (Total=43,785,380 bytes):
     .bss: 1,300,456 bytes (not included in totals)
     .data: 101,768 bytes (0.2%)
     .data.rel.ro: 1,065,224 bytes (2.4%)
     .data.rel.ro.local: 790,024 bytes (1.8%)
     .rodata: 5,927,652 bytes (13.5%)
     .text: 35,900,712 bytes (82.0%)
 
-Showing 41 symbols with total pss: 4036054 bytes
+Showing 43 symbols with total pss: 4036054 bytes
 .text=77.8kb     .rodata=2.52mb     other=1.25mb     total=3.85mb
 Number of object files: 10
 
 First columns are: running total, address, pss
- 2641394 r@Group      2641394 {no path}
-             ** merge strings (count=2)
- 3431298 d@0x2c17740  789904  third_party/container.c
+ 1965409 r@0x266e600  1965409 {no path}
+             ** merge strings
+ 2755313 d@0x2c17740  789904  third_party/container.c
              chrome::mojom::FieldTrialRecorderProxy [vtable]
+ 3431298 r@0x284e518  675985  {no path}
+             ** merge strings
  3500422 t@0x28f1e0   69124   third_party/icu/ucnv_ext.c
              foo_bar
- 3510180 t@Group      9758    {no path}
-             ** symbol gaps (count=2)
+ 3506140 t@0x28f000   5718    third_party/icu/ucnv_ext.c
+             ** symbol gap 0
+ 3510180 t@0x2a1000   4040    third_party/container.c
+             ** symbol gap 1
  3510628 t@0x28f000   448     third_party/icu/ucnv_ext.c
              ucnv_extMatchFromU
  3510780 d@0x2de7008  152     third_party/container.c
              base::android::kBaseRegisteredMethods
  3510874 t@0x2a1000   94      third_party/container.c
              blink::PaintChunker::releasePaintChunks [clone .part.1]
  3510930 d@0x2c176f0  56      third_party/icu/ucnv_ext.c
              ChromeMainDelegate [vtable]
  3510986 d@0x2cd8500  56      third_party/paint.cc
              ChromeMainDelegateAndroid [vtable]
@@ skipping 53 matching lines @@
  3511534 b@0x0        131072  third_party/fft_fixed.cc
              ff_cos_131072_fixed
  3511534 b@0x0        131072  third_party/fft_float.cc
              ff_cos_65536
  3511534 b@0x2dffe80  200     third_party/icu/ucnv_ext.c
              SaveHistogram::atomic_histogram_pointer
  3511534 b@0x2dffda0  28      third_party/icu/ucnv_ext.c
              g_chrome_content_browser_client
  3511534 b@0x2dffe84  4       third_party/icu/ucnv_ext.c
              g_AnimationFrameTimeHistogram_clazz