Consider merging https://chromium.googlesource.com/chromium/blink/+/37e72a50b777a7f8aab62526e03aaff56b9984a6 According to my new telemetry-based benchmark, this CL reduces memory usage in Mobile Gmail by 3 MB (at least as simulated by content_shell on Linux). Specifically, the average of three runs dropped from 52.1 MB to 49.2 MB. In looking at profiles of duplicated StringImpl objects from https://src.chromium.org/viewvc/blink?revision=151336&view=revision, we noticed that a large amount of duplicated StringImpl objects contained URLs (particularly data URLs). This CL atomizes the underlying storage in KURL to help us avoid storing duplicate URL strings. Using STRING_STATS, the savings looks more like 400 kB of string data. (The total amount of string visible to STRING_STATS drops from 3305677 bytes to 2912873 bytes.) A 400 kB savings sounds more realistic to me. Here are the before and after STRING_STATS: == Before == String stats for process id 28425: 6319 (99.15%) 8 bit 2692439 chars 2692439 bytes avg length 426.1 54 ( 0.85%) 16 bit 300731 chars 601462 bytes avg length 5569.1 28 ( 0.44%) upconverted 5888 chars 11776 bytes avg length 210.3 6373 Total 2993170 chars 3305677 bytes avg length 469.7 Total savings 2686551 bytes (44.83%) 5 copies (0 atomic) of length 23530 (potential savings: 94120) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAMgAAADICAYAAACtWK... 63 copies (0 atomic) of length 413 (potential savings: 25606) REPLACE INTO cached_conversation_headers (conversationId,isUnrea... 3 copies (0 atomic) of length 9962 (potential savings: 19924) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA+CAYAAADgZd... 3 copies (0 atomic) of length 9638 (potential savings: 19276) data:image/png;base64,R0lGODlhKAAoAPf/AB2pYP/STTuB+OBKPuFLPzh+9D... 4 copies (0 atomic) of length 6230 (potential savings: 18690) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA+CAYAAADgZd... 5 copies (0 atomic) of length 4418 (potential savings: 17672) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA+CAMAAADXuy... 3 copies (0 atomic) of length 5518 (potential savings: 11036) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACgAAABYCAMAAACwAk... 3 copies (0 atomic) of length 5146 (potential savings: 10292) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA+CAYAAADgZd... 2 copies (0 atomic) of length 4890 (potential savings: 4890) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA+CAYAAADgZd... 4 copies (0 atomic) of length 1598 (potential savings: 4794) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAA6CAMAAADWZb... 2 copies (0 atomic) of length 4438 (potential savings: 4438) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAFoAAABaCAYAAAA4qE... 3 copies (0 atomic) of length 1954 (potential savings: 3908) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADwAAAA8CAYAAAA6/N... 3 copies (0 atomic) of length 1854 (potential savings: 3708) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAA6CAYAAADhu0... 3 copies (0 atomic) of length 1834 (potential savings: 3668) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAA6CAYAAADhu0... 3 copies (0 atomic) of length 1806 (potential savings: 3612) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAA6CAYAAADhu0... 2 copies (0 atomic) of length 3542 (potential savings: 3542) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAFoAAABaCAYAAAA4qE... 3 copies (0 atomic) of length 1770 (potential savings: 3540) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAHgAAAA9CAYAAABm8a... 4 copies (0 atomic) of length 1134 (potential savings: 3402) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAFkAAAA8CAYAAAANMh... 3 copies (0 atomic) of length 1662 (potential savings: 3324) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAQCAYAAAB3AH... 3 copies (0 atomic) of length 1610 (potential savings: 3220) data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAA6CAYAAADhu0... == After == String stats for process id 28148: 5765 (99.23%) 8 bit 2390749 chars 2390749 bytes avg length 414.7 46 ( 0.79%) 16 bit 255622 chars 511244 bytes avg length 5557.0 26 ( 0.45%) upconverted 5440 chars 10880 bytes avg length 209.2 5810 Total 2646371 chars 2912873 bytes avg length 455.5 Total savings 2385309 bytes (45.02%) 161 copies (0 atomic) of length 413 (potential savings: 66080) REPLACE INTO cached_conversation_headers (conversationId,isUnrea... 161 copies (0 atomic) of length 38 (potential savings: 6080) REPLACE INTO hit_to_data VALUES(?, ?); 25 copies (0 atomic) of length 102 (potential savings: 2448) Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like ... 9 copies (0 atomic) of length 101 (potential savings: 808) If you are unable to see this message, click here to viewTo ensu... 38 copies (0 atomic) of length 20 (potential savings: 740) image/webp,*/*;q=0.8 314 copies (0 atomic) of length 2 (potential savings: 626) [] 21 copies (0 atomic) of length 28 (potential savings: 560) response_code_set_by_backend 35 copies (0 atomic) of length 14 (potential savings: 476) static-content 49 copies (0 atomic) of length 9 (potential savings: 432) image/png 15 copies (0 atomic) of length 24 (potential savings: 336) public, max-age=31536000 35 copies (0 atomic) of length 9 (potential savings: 306) Yesterday 16 copies (0 atomic) of length 19 (potential savings: 285) main:static-content 22 copies (0 atomic) of length 13 (potential savings: 273) 1; mode=block 11 copies (0 atomic) of length 24 (potential savings: 240) 2001:4860:4001:801::100f 3 copies (0 atomic) of length 106 (potential savings: 212) XXXXXX REDACTED EMAIL TEXT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX... 8 copies (0 atomic) of length 29 (potential savings: 203) Wed, 22 May 2013 01:15:48 GMT 8 copies (0 atomic) of length 29 (potential savings: 203) Thu, 22 May 2014 01:15:48 GMT 3 copies (0 atomic) of length 101 (potential savings: 202) XXXXXX REDACTED EMAIL TEXT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX... 3 copies (0 atomic) of length 101 (potential savings: 202) XXXXXX REDACTED EMAIL TEXT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX... 3 copies (0 atomic) of length 101 (potential savings: 202) XXXXXX REDACTED EMAIL TEXT XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX... From these stats, it appears that this CL is saving memory by reducing copies of data URLs. Notice that many of the remaining copies are of HTTP header values and SQL queries. I'll tackle those in future CLs.
Also see the bug 117425.
You'll probably want to do your own experiments because Blink's KURL now works very differently than WebKit's KURL due to the integration with GURL. This CL might still be a win for you, but I bet the stats will be different.
We've since implemented new URL class.