DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change: there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already implemented in 
  CSSWorkspaceBinding.
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
Review-Url: https://codereview.chromium.org/2931773002
Cr-Commit-Position: refs/heads/master@{#478142}
Committed: https://chromium.googlesource.com/chromium/src/+/96693ab93867d6a24f3262d9cbb0df5cf102202b

[lushnikov, 2017-06-08 15:04:42]

Description was changed from

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage script vs uiSourceCode
association in DebuggerWorkspaceBinding:
- pushSourceMapping: used to add a rawLocation to uiLocation mapping
  for the scripts
- popSourceMapping: used to remove a rawLocation to uiLocation mapping
  from the script (used only in script formatter)
- setSourceMapping: used to establish a uiLocation to rawLocation
  mapping from uiSourceCode to script

These methods have multiple issues:
- the push/pop mappings approach does not allow to control mappings.
  For this reason, the popSourceMapping is almost never used.
- the setSourceMapping is not symmetrical to push/pop source mapping.
  This means that there's no guarantee that:
     rawLocation == UItoRaw(tawToUI(rawLocation))

This patch kills these methods in favor of a more simplistic approach,
implemented in CSSWorkspaceBinding.

BUG=
==========

to

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to row mapping queries mappings in the same order as ui to raw.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding. With this approach
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

[lushnikov, 2017-06-08 15:04:42]

lushnikov@chromium.org changed reviewers:
+ dgozman@chromium.org

[lushnikov, 2017-06-08 15:04:57]

please, take a look!

[lushnikov, 2017-06-08 15:05:03]

The CQ bit was checked by lushnikov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-08 15:05:14]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-08 16:45:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-06-08 16:45:33]

Dry run: This issue passed the CQ dry run.

[dgozman, 2017-06-08 18:37:11]

Description was changed from

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to row mapping queries mappings in the same order as ui to raw.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding. With this approach
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

to

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding. With this approach
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

[dgozman, 2017-06-08 19:12:04]

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html
(left):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html:176:
function testSourceMapping(next)
Please ensure we have a test for breakpoints+sourcemaps.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html:246:
function testSourceMappingReload(next)
Please ensure we have a test that breakpoints in html are restored after reload.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File third_party/WebKit/Source/devtools/front_end/bindings/BreakpointManager.js
(left):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/BreakpointManager.js:182:
if (isIdentity)
Why don't we care anymore?

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File
third_party/WebKit/Source/devtools/front_end/bindings/DebuggerWorkspaceBinding.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/DebuggerWorkspaceBinding.js:120:
console.assert(modelData);
Remove assert.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js:92:
console.assert(scripts.length);
Remove assert.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js:220:
this._boundUISourceCodes.delete(uiSourceCode);
updateLocations here

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js:357:
Bindings.debuggerWorkspaceBinding.addSourceMapping(this);
Move this to ScriptSnippetModel instead.

[lushnikov, 2017-06-08 21:14:24]

Description was changed from

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding. With this approach
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

to

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding.
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

[lushnikov, 2017-06-08 21:14:34]

please, take another look

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
File
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html
(left):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html:176:
function testSourceMapping(next)
On 2017/06/08 19:12:00, dgozman wrote:
> Please ensure we have a test for breakpoints+sourcemaps.

There's a test which covers both reload and sourcemap:
inspector/sources/debugger-breakpoints/debugger-reload-breakpoints-with-source-maps.html

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/LayoutTe...
third_party/WebKit/LayoutTests/inspector/sources/debugger-breakpoints/breakpoint-manager.html:246:
function testSourceMappingReload(next)
On 2017/06/08 19:12:00, dgozman wrote:
> Please ensure we have a test that breakpoints in html are restored after
reload.

There's a test which covers both reload and sourcemap:
inspector/sources/debugger-breakpoints/debugger-reload-breakpoints-with-source-maps.html

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File third_party/WebKit/Source/devtools/front_end/bindings/BreakpointManager.js
(left):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/BreakpointManager.js:182:
if (isIdentity)
On 2017/06/08 19:12:00, dgozman wrote:
> Why don't we care anymore?

Every Bindings.BreakpointManager.Breakpoint has a set of ModelBreakpoints (one
per target), which in turn
have a liveLocation which is updated as the mapping gets changed.

This was added here:
https://chromium.googlesource.com/chromium/src/+/bb30709e356da03e07cb4a090ab1...

I verified that the scenario described in the patchset works fine with this
change.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File
third_party/WebKit/Source/devtools/front_end/bindings/DebuggerWorkspaceBinding.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/DebuggerWorkspaceBinding.js:120:
console.assert(modelData);
On 2017/06/08 19:12:00, dgozman wrote:
> Remove assert.

Done.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js:92:
console.assert(scripts.length);
On 2017/06/08 19:12:00, dgozman wrote:
> Remove assert.

Done.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/bindings/ResourceScriptMapping.js:220:
this._boundUISourceCodes.delete(uiSourceCode);
On 2017/06/08 19:12:00, dgozman wrote:
> updateLocations here

Done.

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
File third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js
(right):

https://codereview.chromium.org/2931773002/diff/1/third_party/WebKit/Source/d...
third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js:357:
Bindings.debuggerWorkspaceBinding.addSourceMapping(this);
On 2017/06/08 19:12:00, dgozman wrote:
> Move this to ScriptSnippetModel instead.

Done.

[lushnikov, 2017-06-08 21:14:40]

The CQ bit was checked by lushnikov@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-08 21:15:15]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dgozman, 2017-06-08 22:25:17]

lgtm

https://codereview.chromium.org/2931773002/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js
(right):

https://codereview.chromium.org/2931773002/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js:370:
* @implements {Bindings.DebuggerSourceMapping}
Remove

[lushnikov, 2017-06-08 22:34:25]

https://codereview.chromium.org/2931773002/diff/20001/third_party/WebKit/Sour...
File third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js
(right):

https://codereview.chromium.org/2931773002/diff/20001/third_party/WebKit/Sour...
third_party/WebKit/Source/devtools/front_end/snippets/ScriptSnippetModel.js:370:
* @implements {Bindings.DebuggerSourceMapping}
On 2017/06/08 22:25:16, dgozman wrote:
> Remove

Done.

[lushnikov, 2017-06-08 22:34:32]

The CQ bit was checked by lushnikov@chromium.org

[lushnikov, 2017-06-08 22:34:32]

The patchset sent to the CQ was uploaded after l-g-t-m from dgozman@chromium.org
Link to the patchset: https://codereview.chromium.org/2931773002/#ps40001
(title: "address comments")

[commit-bot: I haz the power, 2017-06-08 22:35:20]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-09 00:56:07]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1496961272164040,
"parent_rev": "74ece38823b6cb1dccbe5cbd231f73f5c8ebf448", "commit_rev":
"96693ab93867d6a24f3262d9cbb0df5cf102202b"}

[commit-bot: I haz the power, 2017-06-09 00:56:19]

Description was changed from

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding.
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180
==========

to

==========
DevTools: kill DebuggerWorkspaceBinding.{push,pop,set}SourceMapping

Today, there are three methods to manage mapping between scripts and
uiSourceCodes:
- pushSourceMapping: adds a raw to ui mapping for the scripts
- popSourceMapping: removes a raw to ui mapping from the script
- setSourceMapping: establishes a ui to raw mapping from uiSourceCode to script

These methods have a few disadvantages:
- adding mapping per-script is a memory-consuming approach, given how many
scripts DevTools
  occasionally has
- the push/pop API is invalid and does not allow to remove mapping. For this
reason, the 
  popSourceMapping is almost never used.
- existence of a separate setSourceMapping method to setup a backward mapping
means
  that there's no guarantee that:
     rawLocation == ui2raw(raw2ui(rawLocation))

This patch kills the {push,pop,set}SourceMapping methods in favor of a
simplistic approach, already
implemented in CSSWorkspaceBindings:
1. external mappings (Such as snippets and SourceFormatter) are registered via
the 
  DebuggerWorkspaceBidning.addSourceMapping method
2. the raw to ui mapping is:
   - querying external mappings first
   - queries CompilerScriptMapping (sourceMaps)
   - queries ResourceScriptMapping (regular mapping)
   - queries DefaultScriptMapping (VM UISourceCodes)
3. the ui to raw mapping queries mappings in the same order as raw to ui.
   
Additionally, with the new persistence, mappings are never actually change:
there's 
*ALWAYS ONLY ONE* mapping which controls both lifetime and mapping of each
UISourceCode.
This means that the DebuggerWorkspace.SourceMappingChanged event is not needed.

To sum up, this patch:
- kills push/pop/set methods in favor of a simplistic approach, already
implemented in 
  CSSWorkspaceBinding.
- gets rid of DebuggerWorkspaceBinding.SourceMappingChanged event. It's not
needed since mappings
  never actually change
- cleans up the DebuggerSourceMapping interface: there's no more need for the
isIdentity and 
  uiLineHasMapping methods.

R=dgozman
BUG=670180

Review-Url: https://codereview.chromium.org/2931773002
Cr-Commit-Position: refs/heads/master@{#478142}
Committed:
https://chromium.googlesource.com/chromium/src/+/96693ab93867d6a24f3262d9cbb0...
==========

[commit-bot: I haz the power, 2017-06-09 00:56:21]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/src/+/96693ab93867d6a24f3262d9cbb0...